The present invention relates to a water-thinnable coating composition comprising binders, inorganic pigments, and, if desired, organic pigments and also further customary additives such as solvents, fillers, plasticizers, stabilizers, wetting agents, dispersing auxiliaries, levelling agents, defoamers, catalysts and also further additives, individually or in a mixture with one another, and comprises at least one phosphoric ester and at least one fatty alcohol alkoxylate.

The invention relates to water-dilutable coating compositions comprising binders, aluminum pigment, and an aqueous diluent.
Water-thinnable coating compositions comprising binders, aluminum pigment and an aqueous diluent are known and are intended for use in particular in the finishing of automobiles, for producing metallic coating systems.
Metallic coating systems are nowadays applied preferably by the so-called basecoat/clearcoat technique, in which a basecoat pigmented with aluminum pigments is applied first and then coated over with a clearcoat.
A particular problem of aqueous coating compositions for producing metallic coating systems is that they often have a pH which is so high that the aluminum pigments used react with water, forming hydrogen. This phenomenon results in a range of problems, especially when the coating materials are stored in closed containers.
A range of processes have been disclosed by means of which aluminum pigments are to be passivated in such a way (cf. e.g. EP-A-0581235) that no hydrogen at all, or only a very small amount, is evolved. All of these processes, however, have the disadvantage that the gassing stability is still not satisfactory. With the use of known aluminum pigments passivated by chromation, it is necessary to accept impairments in the shade and metallic effect (flop) of the metallic coating systems.
The object on which the present invention is based is to provide a water-dilutable coating composition comprising binders, inorganic and, if desired, organic pigments and also further customary additives such as solvents, fillers, plasticizers, stabilizers, wetting agents, dispersing auxiliaries, levelling agents, defoamers, catalysts and further additives, individually or in a mixture with one another, which do not have the aforementioned disadvantages of the prior art.
This object is achieved in accordance with the invention by said coating composition comprising at least one phosphoric ester and at least one fatty alcohol alkoxylate.
The water-dilutable coating compositions of the invention can in principle comprise all binders suitable for water-dilutable coating compositions.
Binders which can be used include, accordingly, both refined natural products, examples being products of rosin and oils or cellulose nitrates, and resins whose composition is entirely synthetic. The latter includes phenolic resins, amine resins (e.g., urea resins, melamine resins), alkyd resins, polyvinyl acetates, epoxy resins, polyurethane resins, polyester resins, rosin-modified phenolic resins, chlorinated rubbers, chlorinated polypropylene, cyclorubbers, ketone resins, and acrylate resins.
Binders used in particular are water-dilutable or water-dispersible polyurethane resins, polyacrylate resins, polyester resins and amino resins, which can be prepared in organic solution, and also mixtures thereof.
The polyurethane resins which can be used as binders are known in principle. Suitable examples are the polyurethane resins described in the literature for use in water-based coating materials, provided these polyurethane resinsxe2x80x94in a modification of the preparation described in the respective literaturexe2x80x94can be prepared in the form of organic solutions.
Examples of suitable polyurethane resins are the resins described in the following documents: EP-A-355433, DE-A 3545618, DE-A 3813866, and the as yet unpublished German Patent Application DE 4005961.8. For further details of the preparation of the polyurethane resins and examples of suitable compounds, therefore, reference may be made to these documents.
The polyacrylate resins used as binders are likewise known and are described, for example, in DE-A 3832826. Suitable resins are general water-thinnable or water-dispersible polyacrylate resins which can be prepared in the form of organic solutions.
Also suitable as binders are water-dilutable or water-dispersible polyester resins which can be prepared in the form of organic solutions. Use is made, for example, of corresponding commercially customary water-dilutable or water-dispersible polyester resins, and also the polyester resins commonly used in water-based coating materials.
Further suitable binders include water-dilutable or water-dispersible amino resins. Preference is given to the use of water-dilutable melamine resins. These are, generally, etherified melamine formaldehyde condensates.
Apart from the degree of condensation, which should be as low as possible, the water-solubility of the amino resins depends on the etherifying component, with only the lowest members of the alcohol or ethylene glycol monoether series giving water-soluble condensates. The greatest importance is possessed by the methanol-etherified melamine resins. With the use of solubilizers, butanol-etherified melamine resins can also be dispersed in an aqueous phase. A further possibility is to insert carboxyl groups into the condensate. Transetherification products of highly etherified formaldehyde condensates with oxycarboxylic acids are soluble in water following neutralization, by way of their carboxyl groups, and may be present in the base paints.
As binders it is of course also possible to use mixtures of the aforementioned binders and, in addition or alone, other water-dilutable or water-dispersible binders.
The coating compositions of the invention can comprise customary additives such as solvents, plasticizers, stabilizers, wetting agents, rheological auxiliaries, dispersing auxiliaries, levelling agents, defoamers and catalysts, and also additives individually or in a mixture in the customary amounts. These substances can be added to the individual components and/or to the mixture as a whole.
The coating compositions of the invention can comprise, besides water, the customary solvents, examples being aliphatic or aromatic hydrocarbons, mono- or polyhydric alcohols, ethers, ethers, glycol ethers and esters thereof, and ketones, such as for example, toluene, xylene, butanol, ethyl glycol or butyl glycol (=ethylene glycol monoethyl or monobutyl ether) and acetates thereof, butyldiglycol (ethylene glycol dibutyl ether), ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, cyclohexanone, methyl ethyl ketone, acetone, isophorone, or mixtures thereof.
Further components which may be added to the basecoats of the invention include crosslinked polymeric microparticles, as are disclosed, for example in EP-A-38 127, and/or customary organic or inorganic additives. For instance, examples of effective thickeners are sheet silicates, water-soluble cellulose ethers, such as hydroxyethyl cellulose, methyl cellulose or carboxymethyl cellulose, and also synthetic polymers having ionic and/or associative groups, such as polyvinyl alcohol, poly(meth)acrylic acid, polyvinyl pyrrolidone, styrene maleic anhydride or ethylene maleic anhydride copolymers and their derivatives, or else hydrophobically modified ethoxylated piperidine and triethanolamine. Particular preference is given to the use of tertiary amines as neutralizing agents, especially dimethylethanolamine, triethylamine, tripropylamine and tributylamine.
The basecoat compositions of the invention can comprise all of the dyes or pigments which are known and are customary in the coatings industry.
Examples of dyes and pigments, which can be organic or inorganic in nature, are titanium dioxide, graphite, carbon black, zinc chromate, strontium chromate, barium chromate, lead chromate, lead cyanamide, lead silicochromate, zinc oxide, cadmium sulfide, chromium oxide, zinc sulfide, nickel titanium yellow, chromium titanium yellow, iron oxide red, iron oxide black, ultramarine blue, phthalocyanine complexes, naphthol red, quinacridones, halogenated thioindigo pigments or the like.
Particularly preferred pigments are metal powders, individually or in a mixture, such as copper, copper alloys, aluminum and steel, preferably aluminum powders, which are used in at least predominant proportion and, specifically, in an amount of from 0.5 to 25% by weight based on the overall solids content of the binders in the coating compositions. Also suitable are customary commercial pearl lustre pigments. It is also possible to conceive of the use of combinations with transparent metal oxide, e.g. iron oxide red, titanium dioxide. Metallic pigments used are commercially customary untreated metal powders and also those which have been specially pretreated for aqueous systems.
The metal powders can also be used together with one or more of the abovementioned nonmetallic pigments or dyes. In this case the proportion thereof is chosen such that the desired metallic effect is not suppressed.
Furthermore, the coating composition of the invention comprises esters of phosphoric acid with alcohols or phenols. Aryl esters, alkyl esters and mixed phosphoric esters are used, as are phosphoric acid derivatives. Examples of suitable phosphoric acid derivatives are known from EP-A-0581235.
It has now been found that the stabilisation of metal pigments, especially aluminum pigments, can be further substantially improved, and thus that it is possible to obtain a long-term protective effect for the metal pigments in aqueous and nonaqueous coating formulations, even under extreme conditions, if the phosphoric esters are used in a mixture with fatty alcohol alkoxylates. In particular, the gassing stability is increased by means of this measure.
Preference is given in accordance with the invention to the use of ethers formed by polyaddition of ethylene oxide; that is, by insertion of one or more xe2x80x94CH2xe2x80x94CH2xe2x80x94O groups in conjunction with an acidic oxygen atom with the aid of ethylene oxide. Suitable substrates are fatty alcohols, alkyl phenols, fatty amines, fatty acids and their amides, fatty acid esters, mercaptans and imidazolines.
The products of the reactions, which are carried out industrially under pressure (from about 1 to 5 bar) at temperatures from 120 to 220xc2x0 C., are linear ethers or polyethers which carry a hydroxyl group at one chain end and a functional group, which is dependent on the starting material, at the other end. The addition of a defined amount of ethylene oxide onto the substrate yields a distribution of homologous ethoxylates, the width of which can be influenced in particular through the choice of catalyst.
It is common to use alkaline catalysts, especially sodium methoxide, which lead to a wide Schulz-Flory homolog distribution, whereas alkaline earth metal salts (e.g., calcium acetate, strontium phenoxide) induce a narrowing in accordance with a Poisson distribution. Acidic catalysts (for example, antimony pentachloride) likewise bring about a distinct narrowing in the homolog distribution.
Particular preference is given in accordance with the invention to the ethoxylates, derived from fatty alcohols, of the general formula ROxe2x80x94(CH2xe2x80x94CH2xe2x80x94O)nxe2x80x94H where n=4-10. The compounds used with preference include the fatty alcohol polyglycol ethers. In addition, alkylphenolpolyglycol ethers are also used.
In accordance with the invention, the phosphoric esters and the fatty alcohol alkoxylates are used in a mixture with one another. The proportion of the mixture is 1-20% by weight, preferably 1-10% by weight, based on the solids content of the pigment to be stabilized. The density of the mixture is 1.02 g/cm3 and its viscosity is 400 mPas.
A mixture of the invention composed of phosphoric ester and fatty alcohol alkoxylate contains preferably 2-98% by weight of phosphoric ester and 2-98% by weight of fatty alcohol alkoxylate, it being possible, optionally, for customary organic solvents, and substances other than the phosphoric ester and fatty alcohol alkoxylate, acting as additives or coating components to be present. It goes without saying that the proportions of the above mixture of the invention always add up to 100% by weight. The mixture contains preferably 20-80% by weight, most preferably 40-60% by weight, for example 50% by weight, of phosphoric ester. Irrespective of this, the fatty alcohol alkoxylate can be present in proportions of preferably 20-80% by weight, most preferably 40-60% by weight, for example 50% by weight. It is preferred if the above mixture is free from the optional components.
The mixture comprising effect pigment, phosphoric ester and fatty alcohol alkoxylate is mixed with the above-described binders, coating auxiliaries, fillers and pigments. First of all the metal slurry is prepared, by introducing bronze and 50% of the solvent used in the slurry as an initial charge and then adding the stabilizer, the remaining 50% of the solvent, then the binder and, finally, the neutralizing agent. This is mixed with the metallic coating. Surprisingly it has been found that the gassing stability is significantly improved, especially when this mode of preparation is followed. Likewise, oxidation phenomena on the surface of the metal pigments are prevented. The graying of the pigment surfaces which is otherwise commonly observed, and the loss of brightness, is no longer observed with the additives of the invention.
In addition to the additives of the invention it is also possible to add further substances which serve for passivation. One example is aluminium pigments obtained by having passivated a lubricant-coated aluminum pigment in an aqueous passivating solution containing chromic acid and a water-soluble glycol ether of the general formula R1(xe2x80x94Oxe2x80x94CHR2xe2x80x94CH2)n OH (R1 is a lower alkyl radical, R2 is either a hydrogen atom or a lower alkyl radical, preferably a xe2x80x94CH3 group, n is a number from 1 to 5) and/or a water-soluble glycol of the general formula HOxe2x80x94(CHR3xe2x80x94CH2xe2x80x94Oxe2x80x94)n H (R3 is either a hydrogen atom or a lower alkyl radical, preferably a xe2x80x94CH3 group, n is a number from 1 to 5) at least 50xc2x0 C., preferably from 60 to 90xc2x0 C., with particular preference about 80xc2x0 C.
In order to obtain pigments having the desired properties, it is necessary to use pigments which have a certain minimum lubricant content. The lubricant content is preferably established in the course of the production process of the aluminum pigments.
Aluminum pigments coated with fatty amines as the lubricant result in passivated pigments which have especially advantageous properties. By fatty amines are meant mixtures of long-chain, predominantly primary alkyl amines, which have been obtained, for example, from fatty acids by way of the associated nitrites by means of reduction.
As the lubricant-coated aluminum pigments it is possible to use commonly known and customary aluminum pigments consisting of aluminum or aluminum alloys, preferably of pure aluminum. Preference is given to the use of aluminum pigments in flake form. The aluminum pigments can be used in the form of the commercially available pastes without further pretreatment.
The passivation of the lubricant-coated aluminium pigments is conducted at at least 50xc2x0 C., preferably from 60 to 90xc2x0 C., with particular preference about 80xc2x0 C., in an aqueous solution which comprises chromic acid and a water-soluble glycol ether of the general formula R1(xe2x80x94Oxe2x80x94CHR2xe2x80x94CH2)n OH (R1 is a lower alkyl radical, R2 is either a hydrogen atom or a lower alkyl radical, preferably a xe2x80x94CH3 group, n is a number from 1 to 5) and/or a water-soluble glycol of the general formula HOxe2x80x94(CHR3xe2x80x94CH2xe2x80x94Oxe2x80x94)n H (R3 is either a hydrogen atom or a lower alkyl radical, preferably a xe2x80x94CH3 group, n is a number from 1 to 5).
The aqueous solution may additionally include further additives which have a positive influence on the chromation process, such as, for example, fluorides or phosphates.
Particularly good results are obtained if the passivating solution contains chromic acid and n-butyl glycol (CH3xe2x80x94(CH2)3xe2x80x94Oxe2x80x94CH2xe2x80x94CH2xe2x80x94OH).
Both the concentration of chromic acid and the concentration of glycol or glycol ether can be varied within wide limits. The passivating solution of the invention generally contains at least 1.5, preferably from 1.5 to 4.0, with particular preference from 2.0% by weight of chromic acid and from 3 to 30, preferably from 7 to 15, with particular preference 10% by weight of water-soluble glycol ether and/or water-soluble glycol.
The passivation is preferably conducted in the freshly prepared passivating solution and is concluded in general after from 10 to 30 minutes.
Following the end of passivation, the passivated pigment obtained is separated from the passivating solution and washed thoroughly with water. The passivated aluminum pigment thus obtained can then be incorporated into water-dilutable coating compositions in accordance with methods which are common knowledge.
The water-dilutable coating compositions of the invention are preferably used as basecoat compositions for producing basecoat/clearcoat metallic coating systems. They display excellent stability with respect to hydrogen evolution, and yield metallic coating systems which are comparable in terms of their visual (flop, shade) and technological (moisture insensitivity, condensation resistance, intercoat adhesion) properties, with coating systems produced using conventional (i.e., containing exclusively organic solvents as diluents) basecoat compositions.
The applicability of the coating compositions of the invention is not restricted to the finishing of automobiles. It is also possible to coat other substrates consisting of untreated or pretreated metal, wood, plastic or the like in a one-coat or multicoat process.
The PH of the coating composition can be from 7.5 to 8.5.


The invention pertains to a novel composition comprising guaifenesin tannate and to a method for preparing guaifenesin tannate by reacting guaifenesin with tannic acid at a temperature above the melting point of guaifenesin. The guaifenesin tannate has extended release properties and is useful in pharmaceutical compositions as an expectorant in warm-blooded animals or as a muscle relaxant in non-human animals.

The invention pertains to guaifenesin tannate and its method of preparation as well as pharmaceutical compositions containing guaifenesin tannate.
Guaifenesin is a well-known commercially available compound. It is frequently referred to as guaiphenesin or glyceryl guiacolate. Its chemical name is 3-(2-methoxyphenoxy)-1,2-propanediol. It is a solid having a melting point of 78.5xc2x0 C., and its molecular formula is C10H14O4. It is only slightly soluble (i.e, about 5 wt. %) in water, but is readily soluble in alcohols such as methanol, ethanol, isopropanol, etc. By way of further identification, its CAS number is 93-14-1.
Guaifenesin finds its principal use as an expectorant for promoting or facilitating the removal of secretions from the respiratory tract in a warm-blooded animal, principally a human being. It helps to loosen phlegm (mucus) and thin bronchial secretions to rid the bronchial passageways of bothersome mucus, drain bronchial tubes and makes coughs more productive. It is typically administered to human beings in need of such medication in the form of tablets and/or suspensions.
Guaifenesin has also proven useful as a central nervous system muscle relaxant for non-human warm-blooded animals, particularly horses and cattle. For animals in need of a muscle relaxant, guaifenesin is typically administered in injectable form.
In recent years, research has indicated that guaifenesin may be useful for alleviation of the symptoms of fibromyalgia syndrome and chronic fatigue syndrome. If such research proves that guaifenesin does in fact alleviate the symptoms of FMS and CFS, it will be a very welcome adjunct in the treatment of these syndromes which are quite painful.
In contradistinction to the antihistamines of which many are unstable in the form of their free bases, guaifenesin is relatively stable. Therefore, little, if any attention, has been paid in recent years to improving guaifenesin compositions. On the other hand, there is a considerable amount of prior art which has emerged in recent years which has been directed to salts of antihistamines, principally tannate salts, which stabilize the antihistamine bases. For example, see U.S. Pat. Nos. 5,599,846; 5,663,415; 6,037,358; 6,287,597; and 6,306,904.
Tannic acid is commercially available and is used in many industrial applications. It is frequently referred to as gallotannic acid, gallotannin; glycerite or tannin. It is a pale tan powder having a decomposition point of 210-215xc2x0 C., and is highly soluble in water and alcohols. Its molecular formula is C76H52O46; its CAS number is 1401-55-4. Tannic acid is typically produced from Turkish or Chinese nutgall and has a complex non-uniform chemistry and typically contains about 5-10 wt. % water.
As mentioned above, guaifenesin, in contradistinction to the antihistamines, is quite stable and therefor would not require the addition of a material such as tannic acid to render it stable. However, guaifenesin does have one drawback: it is readily absorbed in the patient""s body, but its action is relatively short-lived. Indeed, its plasma half-life is only one hour. Accordingly, while it provides relatively quick relief to the patient, the patient is required to take relatively high doses several times a day until the condition which necessitated the administration of the guaifenesin has been alleviated. This presents a particular problem to the patient suffering from chronic bronchitis who is therefore required to be on a constant regimen of guaifenesin, thereby increasing the likelihood of the occurrence of undesirable side effects.
It would be very desirable if a form of guaifenesin was available which would have extended-release properties, i.e., the guaifenesin would be slowly released into the patient""s bloodstream over a prolonged period of time. Thus far, the only slow-release forms of guaifenesin which are available are those such as polymer coated tablets. Such prior art formulations provide mixed results in that the guaifenesin is not available for adsorption into the patient""s bloodstream until the polymeric coating has been dissolved, but thereafter the guaifenesin is quickly absorbed and metabolized. The result is that frequently, the guaifenesin must again be administered to the patient within the period of only a few hours.
It has now been found that it is possible to provide an extended-release form of guaifenesin by reacting it with tannic acid so as to form a novel composition hereinafter referred to as guaifenesin tannate.
The guaifenesin tannate is prepared by a method involving the following steps:
(a) heating guaifenesin to a temperature above its melting point; and
(b) slowly (e.g., over a period of 5-30 minutes) adding tannic acid to the molten guaifenesin, while agitating the reaction mixture.
It is not necessary to have any water or other diluent present during the reaction between the guaifenesin and the tannic acid (indeed, tannic acid itself contains about 5-10 wt. % water). Step (b) is carried out while the guaifenesin is maintained at a temperature in the range of about 80 to about 100xc2x0 C., preferably 85 to 95xc2x0 C. After the tannic acid has been added, the reaction mixture is agitated for an additional period of time (10 minutes-2 hours) while maintaining the temperature in the range of about 80 to about 100xc2x0 C. and the reaction mass is thereafter cooled to room temperature. The solid reaction mass comprising the guaifenesin tannate is preferably thereafter milled to form a free-flowing powder preferably to a particle size of about 50 to about 200 mesh. The molar ratio of the guaifenesin to the tannic acid is in the range of about 3 to about 10, preferably, 4 to 7, moles of guaifenesin per mole of tannic acid. It has been found that using less than 3 moles of guaifenesin per mole of tannic acid results in an incomplete reaction, while the use of more than 10 moles of guaifenesin per mole of tannic acid results in a sticky, hygroscopic reaction mass which is difficult to convert into a free-flowing powder.
It would have been expected that the guaifenesin tannate product resulting from the two step method described above would have the structure of an ester since the reaction involves an alcohol, i.e., guaifenesin which is a diol, and an acid, i.e., tannic acid. It is well known that in the course of a typical esterification reaction, water is formed as a by-product. However, it was found that in the course of the reaction between the guaifenesin and the tannic acid, water was not produced as a by-product. Accordingly, it is believed that the guaifenesin tannate is a complex.
The guaifenesin tannate of the invention has the following physical properties: It has a softening point in the range of 57 to 62xc2x0 C., in contradistinction to the melting point of 78.5xc2x0 C. for guaifenesin and 210-215xc2x0 C. decomposition point for tannic acid.
The guaifenesin tannate of the invention is a light-tan colored powder which is soluble in water and alcohols, but is insoluble in methylene chloride, chloroform or toluene. In contradistinction thereto, guaifenesin is a white powder which is soluble in water, alcohols and methylene chloride and sparingly soluble in toluene, while tannic acid is a tan-colored powder which is soluble in water and alcohols, but is insoluble in methylene chloride, chloroform or toluene. Further proof that the guaifenesin tannate of the present invention is a new material and not a physical mixture of guaifenesin and tannic acid has been obtained by the use of FTIR spectroscopy which is discussed in respect to Examples 1-3 below.
The guaifenesin tannate of the invention may be prepared for oral administration in the form of powders, capsules, elixirs, syrups, etc. Preferably the compositions are prepared in the form of tablets containing about 100 to about 500 mg of guaifenesin tannate of the invention per tablet or as a suspension, i.e., liquid, wherein each 5 ml (teaspoon) of liquid would contain about 100 to about 400 mg of the guaifenesin tannate of the invention.
Tablets containing the unique guaifenesin tannate composition of the invention may be prepared in a conventional manner by the addition of suitable pharmaceutical carriers, including fillers, diluents, lubricants and the like as well as conventional and well known binding and disintegrating agents. A typical tablet composition of the present invention will contain, in addition to the guaifenesin tannate, microcrystalline cellulose, corn starch, magnesium stearate, croscarmellose sodium and coloring matter.
The suspension formulations of the guaifenesin tannate of the present invention will typically additionally contain citric acid, caramel, glycerin, sorbitol solution, propylene glycol, saccharin sodium, sodium benzoate, flavoring agent and purified water.
When intended for use as a muscle relaxant for non-human animals such as horses and cattle, the guaifenesin tannate of the invention will be administered in injectable form containing about 50 to about 200 mg per ml of the guaifenesin tannate. Each ml of the injectable liquid typically would additionally contain about 25 to 100 mg dextrose (anhydrous), about 10 to about 40 mg propylene glycol, about 5 to about 20 mg of dimethylacetamide (parental grade), about 0.25 to 1 g of edetate disodium and water for injection q.s.
If desired, the guaifenesin tannate composition of the invention may be formulated with other pharmaceutically active ingredients such as antihistamines and antitussives, e.g., chlorpheniramine, brompheniramine, pyrilamine, phenylephrine, ephedrine, pseudoephedrine, dextromethorphan, carbetapentane, carbinoxamine, and the like. Typically, these other active ingredients will be employed in the form of their free bases or their salts, e.g., citrates, maleates, hydrobromides, hydrochlorides, tannates, etc.
Of course, the dosage of the guaifenesin tannate of the present invention, alone or in combination with other pharmaceutically active ingredients to be administered will be dependent on the age, health and weight of the recipient, types of concurrent treatment, if any, frequency of treatment and effect desired.


A composition and method of making an improved sealant is disclosed. The sealant is made from a base polymer material that includes one or more substantially linear vinyl, acrylate, or methacrylate monomers, a hydrolyzable silane that includes one or more substantially linear vinyl, acrylate, or methacrylate silanes to produce randomly dispersed silane functionality throughout the polymer and a second hydrolyzable mercapto silane to cap some polymer chains via a chain transfer reaction, wherein the polymer has a glass transition point lower than 10xc2x0 Fahrenheit and an average molecular weight between about 40,000 and about 500,000. A sealant is made by adding a cross-linking catalyst and other additives to the polymer in such proportions to produce a sealant that cures upon exposure to atmospheric moisture.

The present invention relates in general to the field of moisture curable sealants, and more particularly, to a sealant that is warm-applied, provides green strength and is transformed from a thermoplastic to a non-thermoplastic sealant by curing at room temperature using ambient moisture.
Without limiting the scope of the invention, its background is described in connection with compositions and methods for the use of a sealant that is curable using ambient moisture at room temperature, as an example.
Various sealant compositions are available that may be cured by exposure to atmospheric moisture, such as those that are based on isocyanate-terminated polyurethanes or silicone polymers. Yet another type of sealant is a so-called xe2x80x9chot melt adhesivexe2x80x9d. Typical hot melt adhesives set quickly due to instant cooling after application and thus provide a narrow window of time in which the position of the substrate, such as glass, may be adjusted within the frame after application. Hot melt adhesives also require high application temperatures typically in excess of 300xc2x0 Fahrenheit.
Generally, the choice of sealant products has been determined by a balance between good quality seals and price. Sealants based on isocyanate-terminated polyurethanes, however, are unsuitable for long-term packaging and storage due to their short shelf life, i.e., they tend to harden in situ. Also, isocyanate based sealants suffer from the drawback of limited thermal stability.
Another problem observed with these types of polyurethane polymers is bubble formation, which results from the production of carbon dioxide during the curing process. Also, heat-resistance of the seals formed is only moderate in many cases and UV resistance through glass is poor.
Sealants based on silicone polymers, on the other hand, generally have desirable properties and yield seals of high quality that perform well under many conditions. Silicone-based systems offer both clear sealing and good ultra-violet light stability. Unfortunately, both the polyurethane hot-melts and silicone sealants typically tend to require expensive materials. Silicon sealants may not possess the desired adhesion characteristics when used in connection with some substrates, particularly in high moisture environments. Another drawback of silicon sealants is the fact that they do not provide a substrate to which a coating, such as paint or stains, will adhere. They also cause contamination problems on substrates.
Various moisture-curable compositions are known in the art. For example, U.S. Pat. No. 4,043,953, entitled xe2x80x9cAmbient Temperature Moisture-Curable Acrylic-Silane Coating Compositions Having Improved Potlifexe2x80x9d, discloses an ambient temperature, moisture-curable coating composition that includes as one part an acrylic-silane interpolymer of an ethylene monomer and a vinylalkoxysilane. U.S. Pat. No. 4,707,515, entitled xe2x80x9cMoisture-Curable Sealant Compositions,xe2x80x9d discloses a sealant composition capable of curing using atmospheric moisture formed from a reaction of substantially linear acrylate ester polymer with a hydrolyzable silane having an amino functional silane group. U.S. Pat. No. 4,147,685 and U.S. Pat. No. 4,177,301, entitled xe2x80x9cAdhering Silicone Compositions,xe2x80x9d and xe2x80x9cPrimer Compositions for Adhering Silicone Compositionsxe2x80x9d, respectively, disclose primer compositions that are the reaction product of methyl- or butylmethacrylate or butylacrylate and an acrylate functional silane that is moisture curable at room temperature. Wakabayashi, U.S. Pat. No. 4,910,255, entitled xe2x80x9cCurable Compositionxe2x80x9d, discloses a composition containing a copolymer that has silicon-containing functional groups capable of cross-linking by forming siloxane bonds, alkyl acrylate monomer from 1 to 8 carbons, and alkyl acrylate monomers with at least 10 carbons as a co-reactant with a silane terminated polyoxypropylene based polymer.
None of the previously mentioned patents disclose materials in which a second silane groups is used to cap some of the polymer chains. As a result of the inclusion of this second type of silane unit, the composition claimed here meets the need for a sealant with desirable physical properties not found in the prior art.
What is needed is a sealant composition curable by atmospheric moisture, that forms a resilient seal at ambient temperatures and that is manufactured with inexpensive raw materials. The sealant composition must also have a desirable combination of properties, such as, convenient application, and a long storage life. Another preferred feature of a sealant is that it provides an opportunity for re-seating the materials in case its position is not exact or an alternative position is preferred, and that is capable of curing using atmospheric moisture. The sealant must also be produced in a cost-effective manner. The sealant formulation of the current invention meets all of these criteria.
The moisture curable composition of the present invention may be warm applied or may be applied as a low viscosity solvent-containing sealant under ambient conditions. When warm applied, the present invention differs substantially from xe2x80x9chot meltxe2x80x9d sealants in that the method of curing the sealant of the present invention does not depend on temperature. As distinguished from xe2x80x9chot meltxe2x80x9d sealants, the sealant of the present invention for warm application is stored as a viscous semi-solid that is warmed to increase mobility. Therefore, the warm applied sealant is not melted and hardened when it cools, as is the case with xe2x80x9chot meltxe2x80x9d sealants. The sealant of the present invention cures when exposed to atmospheric moisture to form a non-thermoplastic sealant, which is highly elastic and adhesive.
The warm applied sealant of the present invention cures chemically, not thermally, and is stable in the warm form as compared to conventional moisture curing hot melt sealants based on polyurethane chemistry. The sealant is produced by admixing a polymer with various additives that produce a sealant with superior green strength and curability. Unlike conventional hot melt sealants, the warm-applied sealant of the present invention allows for repositioning of substrates after application and prior to chemical curing to a non-thermoplastic rubbery sealant.
The curable, warm-applied composition of the present invention is useful for many purposes such as sealant adhesives, pressure-sensitive adhesives, water proofing agents, sealant compositions, casting rubber materials and foaming materials. Using the moisture curable composition of the present invention, the inventors have sealed windows in compliance with the AMAA""s guidelines for sealants. The present composition and method for curing a sealant includes mixing the components in a relatively moisture-free condition. Once blended, the composition may be stored for a prolonged period at ambient temperature without degradation in a sealed container. The composition of the present invention cures rapidly to form a good rubber elastomer upon exposure to atmospheric moisture.
The curable composition of the present invention is used as a one-component elastomeric sealing material that displays superior weather resistance, may be transparent or pigmented and have high tensile strength and elongation. The composition of the present invention readily accepts paint, which is in contrast to silicone-based sealants, which do not. It also displays greatly improved characteristics for use as a highly elastic sealant in window creation and packaging and other areas.
The moisture curable composition of the present invention may be used as a waterproofing agent. It also exhibits a good balance between breaking strength, elongation, and glass transition temperature, while at the same time having a long storage life and improved application during manufacturing as compared to products prepared by existing techniques using more expensive components.
The curable composition of the present invention may also be used as an adhesive because it exhibits high bond strength, in particular, a good balance between peeling bond strength and shearing bond strength, and therefore holds promise for application as a bedding sealant in the formation of large and small windows.
The present invention includes a flowable sealant composition for use in window pane sealing includes a fluid polymer material that is a reaction product of a substantially linear polymerized linear vinyl, acrylate and methacrylate monomers in a free radical process having a viscosity in the range of about 1000 to 50,000 Centipoise measured at 77 degrees Fahrenheit in 70% toluene, and a glass-transition temperature (Tg) not greater than about 10 degrees Fahrenheit (xe2x88x9212.2 degrees Centigrade) with at least two hydrolyzable silanes having organo-functional group(s). The silane and linear monomers are selected and used in quantities that provide a fluid polymer. The polymer is generally homogeneous having an average molecular weight of between about 40,000 and 500,000 Mw.
The polymer is then formed into a sealant by the addition of a crosslinking catalyst to form a sealant that is curable by exposure to atmospheric moisture and that forms a resilient solid. Other additives, such as rheology control agents may be added to control the features of the sealant, as described herein. An important feature of the invention is the selection of reactants for the polymer and the capping of the polymer using, e.g., a mercaptan-group containing silane.
An important property of the sealant composition is the ability to be applied readily to horizontal or vertical joints, to become cured to a tough resilient condition by exposure to atmospheric moisture and also to provide a seal having good resistance to aging by UV, heat and moisture, and resilience and extensibility in the joint. Some of these properties are dependent on the selection of the substantially linear monomers used to form the polymer.
More particularly, the present invention is a composition and method of making an improved sealant used for sealing, e.g., window panes and glass doors. The polymer used as the base for the sealant may be further defined as polymer composition including one or more substantially linear vinyl, acrylate, or methacrylate monomers reacted with a first hydrolyzable silane having one or more substantially linear vinyl, acrylate, or methacrylate silanes to produce randomly dispersed silane functionality throughout the polymer chain. To this mixture is added a second hydrolyzable mercaptosilane to cap some polymer chains via a chain transfer reaction, and a polymer initiator. The resultant polymer has a glass transition point lower than 10xc2x0 Fahrenheit (xe2x88x9212.2xc2x0 C.) and an average molecular weight between about 40,000 and about 500,000. To make the sealant based on the polymer of the present invention, a cross-linking catalyst is added to the polymer to form a sealant.
Also disclosed is a method of making a polymer suitable for use as a base polymer for a sealant composition, a method for making a sealant composition incorporating the polymer and a method of applying the sealant.
While the making and using of various embodiments of the present invention are discussed in detail below, it should be appreciated that the present invention provides many applicable inventive concepts that may be embodied in a wide variety of specific contexts. The specific embodiments discussed herein are merely illustrative of specific ways to make and use the invention and do not delimit the scope of the invention.
The present invention contemplates compositions and methods for making a moisture curable sealant with increased green strength, adhesiveness and resiliency. The composition includes a base polymer having a glass transition point lower than 10 degrees Fahrenheit and an average molecular weight of between about 40,000 and 500,000. The polymer is initiated by the addition of a free radical generating initiator. Free radical polymer initiators are well known to those of skill in the art and are selected based on the speed, temperature, catalytic target and the like. Used as an example herein is t-butyl peroctoate, which is introduced as a polymer initiator or promoter that catalyzes the polymerization of the monomers into polymer chains.
The base polymer is then mixed with additives and an organotin catalyst to produce a moisture curable sealant that may be warm applied or applied at room temperature in solvent. The sealant of the present invention differs substantially from xe2x80x9chot meltxe2x80x9d sealants in that the method of curing the sealant of the present invention does not depend on temperature. As distinguished from xe2x80x9chot meltxe2x80x9d sealants (such as isocyanate moisture-curable, hot melt sealants) the warm applied sealant disclosed herein is stored as a viscous liquid that is warmed to increase its mobility, not to cause a melting and subsequent hardening of the sealant as is the case with xe2x80x9chot meltxe2x80x9d sealants. Alternatively, the sealant may be include sufficient solvent to have low-viscosity at room temperature and to be applied at under ambient conditions.
The warm-applied sealant disclosed herein cures chemically, not thermally. The sealant is stable in the hot form as compared to conventional moisture curing hot melt sealants based on polyurethane chemistry, which are unstable and may not be readily reheated for further use. The sealant is produced by admixing a polymer with various additives to produce a sealant with superior green strength and curability. Unlike xe2x80x9chot meltxe2x80x9d sealants, the sealant disclosed herein allows for repositioning of a combination of substrates after application and prior to curing.
The ideal window sealant possesses the following properties: adhesion strength, low temperature flexibility, resistance to weathering (i.e., resistance to UV radiation), shelf life and ease of application. In addition to these important features, a window sealant is also expected to have sufficient green strength to provide proper stability to the seal between application and complete curing.
Low temperature flexibility is a key requirement for window sealants, as windows tend to flex under wind-loading. Furthermore, as window support structures tend to expand and contract due to thermal variations and flex due to wind-loading, it is desirable for the sealant to maintain its flexibility at both low and high temperatures. The glass transition temperature (Tg) of a sealant is a common indicator of low temperature flexibility.
Another indicator of low temperature flexibility is described by the guidelines of the American Architectural Manufacturer""s Association (xe2x80x9cAAMAxe2x80x9d) for sealants. AAMA requires that windows undergo a low temperature flexibility test, in which a sealant is applied to an aluminum panel is cured, cooled to 7xc2x0 Fahrenheit and then bent 1800 around a one inch mandrel. After bending, the specimens are examined for cracking and loss of adhesion to the aluminum panel.
Resistance to weathering is another important property for a window sealant, as many materials degrade upon extended exposure to UV radiation, becoming brittle, cracked and/or discolored. Another important feature is moisture resistance, especially for use with wooden frames and structures that are susceptible to moisture damage.
Yet another desirable property is coating adhesion. The window sealant must provide a surface that may not only be painted, but that promotes the adhesion of the material to paint. For example, it is well known in the art that silicon-based sealants generally do not provide a surface to which coatings, such as paint, will adhere.
The adhesion of a sealant to a window frame is typically evaluated in two ways. The first is a wind test, in which the glass is secured in the window frame using the sealant, the assembled window and frame are anchored in a retaining frame and the secured window is placed in a wind tunnel or similar device. Positive and negative pressure is applied to the window until the window breaks loose from the frame or fails. The second test used to evaluate the adhesion properties of a sealant to glass is the AAMA""s xe2x80x9cPeel Adhesionxe2x80x9d test, in which the sealant is applied to an aluminum or glass panel, allowed to cure and then peeled away from the panel. The cohesive failure of the strip, in pounds-force per inch of width, is determined and evaluated.
From a manufacturing standpoint, similar features are desired from a window sealant. For example, it is desirable that a window sealant have a long shelf life, that is, the sealant may be cooled and reheated for the next use. The green strength of the sealant is important from the perspective of handling and transporting the windows after assembly. Cure time, shear strength and the rate of strength development during and immediately following the assembly are important to coordinate the throughput of units and storage space. Other physical properties that are indicative of the suitability of a window sealant for a given application are: yield strength, slump, vehicle migration, staining, racking, water resistance and penetration. The methods and quantitation of these results are outlined in the AAMA""s xe2x80x9cVoluntary Specifications and Test Methods for Sealantsxe2x80x9d, relevant portions of which are incorporated herein by reference as to the methods and specifications for testing sealants.
The following are key features that are addressed by the present invention. The present invention provides for a polymer and a sealant that have both a long open time and long shelf life. Heating the sealant facilitates the delivery of the material and does not melt the composition. The heat merely reduces the viscosity of the material to a desirable level for application to a surface for mounting glass. The green strength of the sealant of the present invention is also improved over existing compositions from the perspective of handling and transporting the windows after assembly.
Furthermore, using the base polymer to make the sealant and methods of the present invention, a window sealer with improved cure time, shear strength and the rate of strength development is obtained. Other physical properties that are indicative of the suitability of a window sealant for a given application are: yield strength, slump, vehicle migration, staining, racking, water resistance and penetration.
In order to provide a cured sealant composition having desirable flexibility at temperatures to which the seals may be exposed, it is necessary to make a base polymer for use with the polymer having a glass-transition temperature (Tg) not greater than about 10 degrees Fahrenheit. The Tg of a polymer is generally regarded as the temperature below which the polymer has reduced, and in most cases non-existent, flexibility. The xe2x80x9cTgxe2x80x9d of a polymer is described by Flory, xe2x80x9cPrinciples of Polymer Chemistryxe2x80x9d, pp 56-57 (Cornell University Press), the relevant portions of which are incorporated herein by reference. While the Tg of a given polymer may be measured (e.g. by DSC measurement method), it may also be calculated as described by Fox, Bull. Am. Physics Soc., p. 153 (1956). Examples of Tg of certain polymers are generally known to those of skill in the art with particular reference given by: Brandrup, J and Immergut, E. H.; Polymer Handbook (Wiley).
The molecular weight and viscosity of the polymer is another important consideration for the present invention. If the viscosity of the polymer is too low, the viscosity of the sealant composition made with the polymer base prior to curing may be too low for ease of application, that is, it must be sufficiently viscous to be applied to a window without running or dripping off the window surface during application. As a corollary, if the molecular weight of the polymer is too low, the cured polymer may not be strong enough so that it is not suitable for use as a window sealant.
Highly viscous polymers, however, may lead to use of excessive amounts of solvents or plasticisers or require a high temperature for application. Furthermore, the vicosity and polymerization rate and the features of the base polymer and the final sealant must reduce the risk of shrinkage or weakening of the cured seal. The base polymer for use in the sealant composition will have an average molecular weight (Mw) between 40,000 and 500,000, with a molecular weight of between about 60,000 to 100,000, having particulary useful characteristics. The molecular weight may be determined by gel permeation chromatography using, e.g., a U-Styragel with 105, 104, 103, and 500 Angstrom columns calibrated with polystyrene standards.
It should be noted that those of skill in the art will know that the distribution of molecular weights of a polymer exists in any finite sample of polymer, and the number average molecular weight (Mn) reflects the number average molecular weight of the polymer molecules in the sample measured. The average molecular weight value is an important guide to various properties including, e.g., the tensile strength of the polymer.
Suitable polymers have low viscosities as determined using, e.g., a 70-80% solution in an organic solvent such as toluene or xylene at room temperature. In one embodiment, the polymer material has a viscosity in the range about 1000 to about 50,000 Centipoise as determined using an 70% solution in toluene at room temperature.
Polymer
The invention provides an improved moisture curable polymer composition that is particularly suitable for use as a window sealant. Substantially linear acrylate and methy acrylate monomers such as: lauryl methacrylate, methy acrylate, ethyl acrylate, butyl acrylate, 2-ethyl hexyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate and 2-ethyl hexyl methacrylate, may be used as the major component of the polymer backbone. Alternatively, vinyl monomers such as vinyl acetate, acrylonitrile, methacrylonitrile, styrene, dioctyl fumarate, dioctyl maleate and maleic anhydride may be used as the major component of the polymer backbone.
The major component of the polymer is a mixture of one or more linear, or near linear chain acrylates. The polymer includes a polymer backbone formed from alkyl acrylates that have from 1 to 14 carbons. The flow properties of the sealant are generally dependent to some extent on the linear nature of the alkyl acrylate ester polymer used. Linear acrylate ester polymers will generally be used (e.g., ones that are soluble in methylene chloride, tetrahydrofuran, toluene, xylene and ethyl acetate). Examples of alkyl acrylates that may be used, in varying concentrations relative to each other, are: substantially linear acrylate monomers such as, methyl acrylate, ethyl acrylate, butyl acrylate and 2-ethyl hexyl acrylate. Substantially linear methylacrylate monomers may include: lauryl methacrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate octyl methacrylate and stearyl methacrylate. When using substantially linear vinyl monomers these may include: vinyl acetate, acrylonitrile, methacrylonitrile, styrene, dioctyl fumarate, dioctyl maleate and maleic anhydride. As an example, one ratio that may be used is a 27:31:10 weight to weight ratio of butyl acrylate:methylacrylate:lauryl methacrylate.
A minor amount of branching of the alkyl acrylate is acceptable provided that the flow characteristics of the polymer are not adversely influenced to a significant extent. Acrylate ester polymers, in general, tend to have good aging resistance and are comparatively inexpensive. Preferably, the polymer includes from about 27 to about 70 weight percent of alkyl acrylate components.
Silane functional groups are randomly interposed along the polymer backbone to provide for moisture curing of the polymer. The specific types of alkoxy silanes used for the present invention are important in relation to the materials present in polymer and used for the final cured sealant. Examples of organic silanes that may be used include: vinyl trimethoxysilane, vinyltriethoxysilane, vinyltris(2-methoxyethoxy)silane, 3-[tris(trimethylsiloxy)silyl]propyl methacrylate, vinyl methyldimethoxy silane, vinyl methyldiethoxy silane, vinylphenyldimethoxysilane and vinyl oximino silane. More specifically, it has been found useful to use methyl trimethoxysilane as both a moisture scavenger and crosslinking agent. Vinyl trimethoxysilane is useful for incorporation into the polymer to yield pendant silane side groups which are also capable of forming cross-links. The polymer may include from about 0.23 to about 0.8 weight percent of one or more of these silane components.
To provide for the capping of the polymer chain, and consequently increase the stability and uniformity of the polymer for use in the sealant composition, a mercapto-containing alkoxy silane is used. One example of a polymer capping alkoxy silane is mercaptopropyl trimethoxysilane. The polymer will include from about 0.15 to about 0.40 weight percent of mercaptan silanes selected to provide a terminal functional group and to help control molecular weight.
Examples of silanes that serve as the second hydrolyzable silane for the lateral formation of bonds and interactions between adjacent polymer chains include, but are not limited to, mercaptopropyl trimethoxysilane, mercaptopropyl triethoxysilane, mercaptopropyl tripropoxysilane and mercaptopropyl tributoxysilane.
Representative examples of other organic silane crosslinking/moisture scavenging agents include, but are not limited to, methyltrimethoxy silane, dimethyldimethoxysilane, trimethylmethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, methyltriethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, triphenylmethoxysilane, phenyltriethoxysilane, diphenyldiethoxysilane, vinyltriacetoxysilane, methyltri(dimethylamino)silane, methyltri(N,N-methylethylaminoxy)silane, methyltri(N-methyl-N-acetylamino)silane, methyltri(isopropenoxy)silane, vinyltrimethoxysilane, vinyltriethoxysilane, xcex3-methacryloxypropyltrimethoxysilane, xcex3-methacryloxypropylmethyldimethoxysilane, methyltriacetoxysilane, xcex3-glycidoxypropyltrimethoxysilane, xcex3-aminopropyltriethoxysilane, beta-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, xcex3-aminopropyltrimethoxysilane N-(2-aminoethyl)-xcex3-aminopropyltrimethoxysilane, N-(2-aminoethyl-xcex3-aminopropylmethyldimethoxysilane, N-(2-aminoethyl)aminomethyltrimethoxysilane, dimethoxymethyl-3-pyperazinopropylsilane, 3-piperazinopropyltrimethoxysilane, N-(3-triethoxysilylpropyl)urea, N-phenyl-xcex3-aminopropyltrimethoxysilane and the like, although the present invention is not limited thereto. In addition, partial hydrolysis condensates of the above organic silanes may be used.
Sealant
Sealant compositions according to the present invention are flowable during the window assembly process so that a single application may be used on the window and require no curative agent other than atmospheric moisture. The sealant will generally be a mixture of a polymer base and various additives, as described hereinbelow in Example I, with a sealant cross-linking catalyst or promoter, that adds varying degrees of strength and adhesiveness to the final cured sealant (See Example II). The sealant catalyst or promoter may also be described as one or more additives that accelerate the final cross-linking of the compounded polymer base into a sealant. The sealant catalyst will generally be an organo-tin catalyst.
In use, the final sealant is: (a) provided as a viscous liquid composition having sufficient solvent to provide a sufficiently low viscosity at room temperature for application; or (b) provided as a semi-solid composition that after application at 200-250xc2x0 F. provides sufficient green strength after setting of glass. If kept protected from water or moisture, the consistency of the sealant will remain the same until exposed to humid conditions. The sealant composition cures within a short time with atmospheric moisture, whether as a solvent containing viscous liquid or a warm applied semi-solid solvent version. The cured sealant forms a permanently resilient and pliable product with a Tg between about xe2x88x9250 and 10 degrees F.
The curing rate will dependent on, e.g., the relative humidity, temperature, amount of solvent and the amount of cross-linking catalyst. A desirable cure rate for sealants curing at room temperature is about 5 mm thickness per day, which may be achieved with sealant compositions according to the invention that include a catalyst such as organo-tin compounds. Generally, the catalyst will be provided in an amount sufficient to catalyze the reaction.
Sealant compositions according to the invention include an effective amount of the sealant catalyst, and as described hereinbelow one or more additives. Additives for use in the final sealant include: water scavengers, UV blockers, fillers and rheology control agents (e.g., thixotropic agents (e.g., fumed silica) and wetting agents to enhances thixotropy (e.g., propylene glycol)). In fact, the sealant polymer may provide the major part of the sealant composition, or it may be compounded with quantities of additives according to the desired properties and use of the sealant. The sealant catalyst may be used in conjunction with fillers, solvents, plasticizers, adhesion promoters, or other additives known in the sealant art.
Sealant compositions of the present invention are typically formed in a mixing unit containing a sweep blade and a high speed disperser. The appropriate amount of the polymer prepared (as previously described) is placed in a mixer along with: the crosslinking catalyst such as an organo-tin catalyst that promotes the crosslinking process. In addition, a water scavenger agent (such as methyltrimethoxy silane); a thixotropic agent (such as fumed silica); an epoxy silane cross-linker for curing or a wetting agent (such as propylene glycol for example, that enhances thixotropy), may be added.
Sealants intended for exterior use are expected to encounter temperatures below 0 degrees centigrade. As windows may be used as interior or exterior windows, the present invention was designed and selected to form a sealant based on a polymer having a Tg of between about xe2x88x9250 and about 10 degrees Fahrenheit.
The following examples are provided by way of illustration only, and are not to be construed in a limiting sense.


The invention relates to a semiconductor component which is capable of blocking such as an (IGBT), a thyristor, a GTO or diodes, especially schottky diodes. An insulator profile section (10a, 10b, 10c, 10d, 11) provided in the border area of an anode metallic coating (1, 31) is fixed (directly in the edge area) on the substrate (9) of the component. The insulator profile has a curved area (KB) and a base area (SB), said curved area having a surface (OF) which begins flat and curves outward and upward in a steadily increasing manner. A metallic coating MET1; 30a, 30b, 30c, 30d, 31b) is deposited on the surface (OF). Said coating directly follows the surface curvature and laterally extends the inner anode metallic coating. The upper end of the curved metallic coating (MET1; 30a, 30b . . . ) is distanced and insulated from one of these surrounding outer metallic coatings (MET2; 3) by the surrounding base area (SB) of the insulator profile (10a, . . . , 11) such that an extensively constant course of the line of force which evades extreme values results between both metallic coatings (1, 31, MET1; 3, MET2) when reverse voltage or blocking voltage is applied between the interspaced metallic coatings.

In semiconductor components having at least one blocking p-n junction, the latter appears on the surface of the substrate, on which and in which the semiconductor component is realized, somewhere between the live contacts. In said surfacing areas high electric field strengths, in case the p-n junction is blocking, i.e. a higher voltage is applied to the cathode than to the anode or a controllable semiconductor device is not yet connected through its gate terminal, result in undesired leaking currents flowing between the anode and the cathode, which currents are designated as positive or negative reverse bias current depending on the direction of polarization of the voltage to be blocked or reversed. For reducing that portion of the reverse bias currents, which is caused by high field strengths in the termination portion, so-called xe2x80x9cjunction terminationsxe2x80x9d are employed in the prior art, which, for example in the form of specially formed field plates, cause an optimized course of equipotential lines and thus avoid high field strengths in the termination portion of such components, cf. DE-A 195 35 332 (Siemens), column 3, line 58 to column 4, line 35; or xe2x80x9cMultistep Field Plates . . .xe2x80x9d, IEEE Transactions on electron. devices, Vol. 39, No. 6, June 1992, from page 1514 onwards; xe2x80x9cThe Contour of an Optimal Field Platexe2x80x9d, IEEE Transactions on electron. devices, Vol. 35, No. 5, May 1988, from page 684 onwards; and finally xe2x80x9cTheoretical Investigation of Planar Junction Terminationxe2x80x9d, Solid-State Electronics, Vol. 39, No. 3, pages 323 to 328, 1996. The planar junction terminations described therein are optimized with regard to their geometry, on the one hand as a field plate having steps and on the other hand as an optimized steadily curved field plate having a modified elliptical geometry. However, the prior art has not yet succeeded in economically fabricating the optimized geometric structure of a field plate in the termination portion of a semiconductor component capable of blocking, especially of such a component to which a high voltage of more than 500 V can be applied.
It is the object of the invention to fabricate the aforementioned semiconductor components, which are in particular highly blocking or capable of blocking, on an economic basis, i.e. at low costs, and nevertheless utilize their maximum blocking capacity.
This is achieved by the invention, if a termination portion of the inner anode metallic coating comprises an insulator profile, having a shape which begins flat and is curved outwards and upwards in a steadily increasing manner, which portion is the xe2x80x9ccurved portionxe2x80x9d of the insulator profile, and having a xe2x80x9cbase portionxe2x80x9d, which is located directly adjacent thereto and is virtually planar, said base portion together with the curved portion determining the cross-section of the insulator profile.
The insulator profile is designed such that, between the curved inner metallic coating, outwardly extending the anode, and the outer metallic coating, located outwards of and adjacent to the base portion of the insulator profile, which will in most cases be the cathode, peak values of an electric field generated during operation can be avoided. The insulator profile is produced by a method, in which an at first deposited insulator layer having a thickness is additionally covered with a resist layer over the entire substrate, which resist layer is illuminated through a mask in a structured manner, which mask changes in its gray-tone value in accordance with the desired course of curvature in the curved portion of the respective insulator profile. The gray-tone value in the mask is transferred into the resist layer by exposure, which layer can be structured subsequent thereto, especially by developing, in order to then transfer the structure of the developed resist layer into the insulator layer having a thickness by an etching process, such as RIE (reactive ion etching), wherein it is an advantage if the etching rate of the insulator layer and the etching rate of the resist remainders, remaining after developing the exposed resist layer, are about equal in order to prevent a not-to-shape transfer of the resist profile into the insulator.
The resulting insulator profiles can either surround the anode in the form of a wall or a plurality of insulator profiles may be provided which are arranged in an outwards staggered manner and the curved surface of which is differently shaped. If a plurality of staggered insulator profiles is provided (claim 2, claim 3), the curvature of the surfaces of the curved portions is not equal, but steadily increases with each profile being located further outwards (claim 3).
On the mentioned respective curved surfaces metallic coatings are deposited, which, for the insulator profile outwardly adjoining the inner anode, conductingly pass over into the anode metallic coating.
The structuring, which is coded in its gray-tone value, is performed, during exposure, such that a desired light-intensity profile is coded into the mask by the semitone process, i.e. via a pixel screen, and that the pixel sizes are transferred below the resolving limit of a reducing projection exposure in an almost continuous course of exposure of the resist layer, by which it is thus possible to produce continuous surfaces curving outwards and upwards; the insulator profiles formed according to the invention thus have at least one continuous surface (without steps) steadily extending across a substantial area, which surface is designed in a manner which theoretical calculations for an optimized course of flux lines, when a reverse bias voltage load or conducting-state blocking load is applied, imply to be favorable.
By use of the invention the thickness of the insulator layer can be continuously varied in a process in a predetermined and controlled manner over a wide area of up to 10 xcexcm; it is not necessarily required to give the surface curvature an ideal course as long as it is ensured that the substantial increases of field strength can be avoided and that the reverse bias voltage load at the termination of the anode towards the cathode does not include substantial peak values.
Even with semiconductor components having reverse bias voltages of more than approx. 500 V, the theoretically maximally possible reverse bias voltage can almost be achieved at minimum space requirements for the junction termination, i.e. the xe2x80x9cblocking capacityxe2x80x9d of the occupied space can be fully utilized. The minimum space requirements are important in said components, a plurality of which is produced from one wafer, and wherein utilizing the blocking capacity to a maximally possible extent becomes the more important the higher the reverse bias voltages are. Said aspects are of particularly great importance for highly blocking IGBTs.
Even with Schottky diodes, which are not based on a p-n junction, but which utilize the blocking capacity of a metal-semiconductor junction, the insulator profiles produced according to the invention may be employed in an advantageous manner. At the edge of the metal-semiconductor junction the small effective radii of curvature would result in excessive field increases. For preventing said increases, diffused guard rings are employed in the prior which, however, at strong conducting-state loads, cause an undesired injection of minority charge carriers. By use of the insulator profiles and field plates produced according to the invention such an injection of charge carriers does not occur and the diffusion process during production can be omitted.
The use of the invention, which is limited to measures performed at the surface of the semiconductors, is particularly advantageous even if the power semiconductors are to be improved on the basis of silicon carbide (SiC), as an example for a semiconductor having a high band width (claim 12). In said semiconductors a very low diffusion constant for doting substances must be put up with and this being the reason why termination portions can virtually not be produced by diffusion.
The component, with the insulator profiles produced according to the invention, comprises profiles which, at the transition to the anode, do not terminate in a continuous or steady manner, but terminate with a small step in the order of magnitude of more than 5 nm and less than 50 nm. Said step being very small compared to the thickness of the metallic coating and is virtually of no consequence, but results from the method of production by gray-tone lithography. Thus, the metallic coating may, for example, have a thickness of approx. 1 xcexcm, while the xe2x80x9cstepxe2x80x9d of the insulator at the end of the curved portion of the insulator 20 produced by gray-tone lithography is 20 nm.
Gray-tone lithography works in such a manner that the substrate is covered with an insulator layer, which is at first covered with a photosensitive layer, which is exposed in such a manner that the course of curvature of the surface of the insulator profile is exposed into the photoresist layer by gray-tone variation, i.e. by adapting the light-intensity distribution to the shape of the insulator profile, which photoresist layer is structured subsequent thereto by developing (claim 11). The photoresist layer structured in such a manner now consists of resist remainders only, forming blocks on the insulator layer, which blocks correspond to the insulator profiles. By means of an etching technique, for example a dry-etching process, the resist remainder still present on the substrate surface is conformally etched into the insulator layer, wherein the insulator layer is substantially planely removed and is more extensively removed where there are no resist remainders (claim 6).
The transfer by shape is promoted if the etching rates of the resist remainders and the insulator layer are equal; if they are not equal the shape of the resist remainder must be adapted accordingly, which may be effected by adapting the intensity distribution during exposure.
The height of the insulator profile in the base portion can be selected to be higher or lower (claim 4, claim 5). If the insulator profile has a height of more than approx. 5 xcexcm in the base portion, the slope at the end of the curved portion at the transition to the base portion is more than 10xc2x0. The curved portion ends steeper here than in the insulator profile, which is flat in the base portion (claim 5). In a higher base portion the normal extension of the base portion is substantially ten times the height of the base portion, preferably even more.
If a more flat base profile, which is easier to fabricate by gray-tone lithography, is selected (claim 5), an additional screen electrode, which is located above the anode potential of the inner metallic coating, can be formed above the junction termination. The lateral extension of the base portion is a multiple of the height of the base portion here, in particular more than 50 times to 200 times the height of the base portion, which especially has a height of 2 xcexcm. Between the end of the curved portion and the beginning of the upward curvature of the additional screen electrode (hood) there is an intermediate region, which, in its extension, is adapted substantially to the radius of curvature of the curved lateral outer end of the hood, in which intermediate region the distance between the hood, which follows a substantially horizontal path here, and the surface of the base portion is substantially constant.
The curved portion of the hood is preferably a quarter circle (claim 7). Its curvature can be considerably more pronounced than that of the surface of the curved portion within the base portion of the insulator profile.
The region between the anode metallic coating and the outer cathode metallic coating, i.e. the region of one or more staggered insulator profiles, can be covered in an elevated manner with a wall-like casting compound, in order to prevent flashover (claim 9).
If insulator profiles arranged in an outwards staggered manner are provided (claims 2, 3), below each of the staggered metallic coatings, extending beginning from the outer end of the base portion of the insulator profile located further inwards up to the upper end of the curved portion of the base profile located further outwards, a strip-shaped compensating area can be provided in the substrate, which is diffused into the substrate and which transfers the potential present at the respective location when a voltage is applied from the substrate area to the respective metallic coating (claim 10). The doting of said strip-shaped zones diffused into the substrate substantially corresponds to the doting which is selected for a p+ region below the anode metallic coating.
The penetration depth of the diffused zones below the metallic coating is preferably only low, preferably less than 10 xcexcm, which technologically does not give rise to field peaks. The p+ diffusion zones transfer their potential to the respective metallic coating curving outwards and upwards (away from the substrate).
The lateral extension of the metallic curved portions should be adjusted to the space-charge depth and at the same time correspond to twice to three times the space-charge depth.

Optimized border of semiconductor components

Fraunhofer-Gesellschaft zur Foerderung der angewandten Forschung e.V.


A control apparatus for a self-moving cart is disclosed, in particular a golf caddy, comprising at least a speed control of a motor onboard the cart and a logical control unit which adjusts said speed control of said motor based on the relative position of a reference user, furthermore comprising a proximity detection device meant to face the rear side of the cart, with respect to the travelling direction, so as to detect a relative distance with respect to a user following the cart, said logical control unit being configured so as to determine said speed control depending on said detected relative distance so that it is maintained in a tolerance range defined by a maximum distance and a minimum distance, wherein said minimum distance is such as to enable the user to operatively reach on/off means of said apparatus meant to be installed onboard said cart.

Self-moving carts are known, provided with small independent motors (electric-battery motors, small combustion engines, . . . ), which are employed for transporting objects or work/sport equipment on rough terrain, in the presence of an operator who walks alongside controlling speed and direction thereof. A particularly widespread application, on which the following description will be mainly based, is that of golf caddies, that is electric-drive caddies for transporting golf bags.
Golf caddies are normally provided with three or four support wheels, of which the driving one/s are controlled by one or two (in order to have two independent motor shafts) battery-powered electric motors. These caddies are conceived to save the golf player from carrying on his/her shoulder his/her bag containing the clubs and all the items required for playing (balls, tee, . . . ), which may weigh up to 20 kilograms, along the various kilometers which are walked when completing a golf game.
Although motorless carts also exist, self-moving ones have an undeniable advantage, as they save the golf-player from the effort of pushing or dragging the cart on usually rough and sometimes muddy and irregular playing fields.
The self-moving golf caddie is essential for people who would not be strong enough to carry along or push the golf bag and in any case it is very useful also for those who would have the physical strength but who can save energies for the game.
However, the provision of a drive on golf carts implies various problems. One of the most significant ones is that of adjusting the caddy speed to adapt it to that of the moving player, in particular because he/she continuously accelerates, slows down and stops on the golf course, both to play when it is his/her turn, and to wait for game companions when it is their turn.
In substance, as it can be guessed, a significant problem of self-moving carts is that of causing them to follow the movements of the respective player in as regular a way as possible.
A first type of known cart, of a simpler and cheaper construction, provides a manual control device arranged on the guiding handle. Thereby, the player always maintains contact with the caddy handle, which enables him/her to guide the movement direction, so he/she can simultaneously act on the controls which are mounted on the handle, within easy reach. In this case, the control device comprises at least a switch, to switch the motor on and off, and a speed adjuster, usually in the shape of a small wheel or other mechanical device which acts on motor speed.
This solution is inexpensive and reliable, also because the player always maintains caddy guidance, but the adjuster requires continuous and meticulous handling, to adapt the caddy pace to the player's, which is at least inconvenient. Moreover, in case a mistake is made in adjusting the speed (humidity may cause contact with the adjuster to become slippery) or contact with the caddy is lost (for example due to a snag), caddy control may be lost, with the risk of damaging the golf course or the equipment.
Summing up, this control mode causes an unpleasant distraction to the player and problems for the speed setting and possibly for the direction to be imparted to the caddy, which must be continuously manually adjusted.
As electronics costs and dimensions drop and as the calculation power of electronic circuit boards increases, it has been possible to offer semi-automatic or fully automatic golf caddies; they solve the problems set forth above, moving independently on the ground, without physical contact being required between the player and the caddy and without the player having to actively set the caddy speed.
All the solutions known so far start from the approach that the cart must follow the player during his/her movements on the golf course. Therefore, the control system provides a receiver/transmitter, two-unit apparatus, partly mounted onboard the cart and partly carried by the player. The two units exchange signals transmitted through the air (on various wavelengths and with various powers, depending on the circumstances) so that the relative position thereof may be determined and a control may be sent to the cart drive to follow the unit which the player carries with him/her. Examples of these known systems are described in U.S. Pat. No. 3,742,507, U.S. Pat. No. 3,472,333, U.S. Pat. No. 3,812,929, U.S. Pat. No. 4,844,493, U.S. Pat. No. 5,611,406, U.S. Pat. No. 5,711,388, WO201359423, EP2021823.
In some cases it is also resorted to a player's position signal detected with GPS technology.
However, all these solutions, in which the cart follows the player, imply a variety of problems:
a. the transmission system and the track-and-follow logic is expensive to accomplish and necessarily requires an electro-mechanic steering system or double motor for changing direction, because the cart is independent and must be able to steer automatically;
b. the control system is not applicable to existing manual carts, but at a higher cost than the cart itself;
c. The player is forced to carry with him/her a control unit which identifies him/her univocally, to allow the cart to follow the correct player; the individual portable units must hence be always maintained with the relative cart or preliminary programming to the use of the cart must be made by the user, which is certainly a problem in large golf clubs (where a plurality of carts are always kept at the players' disposal);
d. cart independence may lead it to go through not-allowed areas (such as the greens and the bunkers), narrow passages (small bridges, bottlenecks, . . . ) or bumpy paths (potholes, soft ground, . . . ), with the imaginable consequences;
e. the following distance, with which these systems work best, may cause the cart trajectory to intercept obstacles or other players;
f. if the cart stops due to an obstacle (a rock, a ditch, yielding ground, . . . ), the player does not realise it immediately and may walk away by a fair distance before having to walk back to collect the equipment.
Other proposed solutions for directing and moving golf carts at controlled speed provide to act with a traditional remote "guiding" system, that is, through a remote control (see for example U.S. Pat. Nos. 3,472,333, 3,720,281, 3,742,507, 3,812,929, 3,856,104, 3,976,151 and 4,109,186). In this case some of the problems illustrated above are solved, but the further problem of the difficulty of use is introduced.
Another disadvantage which all these track-and-follow or remote-control systems share is the fact that the user no longer comes into physical contact with the cart during the movement thereof. That fully removes a possible dragging effect, which some player has learnt to exploit, that is, the opportunity of being partly dragged by the cart, using the traction power of the wheels, especially when raised sloping areas must be approached.
An alternative consists in carts provided with proximity sensors facing towards the rear travelling side, that are moving preceding the player who follows. An example of these technical solutions is disclosed in FR2868560.
However, the control mode of the known solutions is not satisfactory yet. In particular, the use of some types of sensors does not provide a fully reliable signal, which makes these systems virtually unusable in practice.
Firstly, in order to propose a commercially acceptable system, it is necessary to employ modestly-priced sensors, which intrinsically provide signals subject to errors and disturbances; since cart control is rather critical, in order to be able to precede in a regular way the player at a short distance, any assessment mistake may lead to an unpleasant dynamic behaviour. In particular, prior-art systems are subject to control instability (elastic effect) which prevent the cart from synchronising with the player's speed.
Moreover, operation limits exist linked to the nature of the sensors.
For example, when the sensor is of the sonar type (that is, ultrasound), false readings may occur in case of strong wind, ice, dust, and/or high-pitched background sounds, which may gripper the uncontrolled start of the cart (safety problems). Moreover, when the user wears sound-absorbing garments (such as sponge-like piles or thick woolen jumpers, the sonar sensor does not correctly detect the distance and the cart does not move at all or very irregularly (movement smoothness problems). If the garments are loose or not perfectly perpendicular to the sensor, the sensor may detect measurements which differ up to 10 cm from the actual one. Finally, should the user move only his/her hand close to grab the cart handle, the ultrasound sensor may detect a general sudden approaching of the player and suddenly accelerate cart speed in an undesired manner.
When instead the sensor is of the infrared type, false readings easily take place depending on the temperature of the surrounding objects; on golf courses, outdoors, it is very likely that an infrared sensor is hit and saturated by direct sunlight, which produces an incorrect signal and imposes undesired movements to the cart.

Control system of a self-moving cart, in particular a golf caddie


An improved method for inhibiting the deposition of adhesive contaminants, hot melts and/or pressure sensitive adhesive materials onto the surfaces of secondary paper products and repulping equipment during the manufacture of same from waste paper products comprises the application of a water-soluble dispersant selected from the group consisting of a hydrophobically modified hydrocolloid or an acrylic acid polymer. The dispersant, preferably a modified guar gum or sodium acrylic acid/maleic acid copolymer improves product quality and papermaking equipment performance.

The recycling and transformation of waste paper materials into secondary paper products is important from an environmental standpoint as well as an economical one. Not only does it save natural resources and reduce volumes of trash and pollution, but if carried out in an efficient manner, utilizes an inexpensive source of paper filler. However, a number of problems must be overcome in the successful transformation of waste paper materials to secondary paper of suitable quality and performance.
The secondary fiber industry utilizes waste paper or paper products as a source of paper fiber (commonly referred to as "secondary fiber") to produce finished paper products. Waste paper and paper products that are the source of the secondary fiber include any waste paper materials such as newspapers, books magazines, waste bags and boxes, mixed office waste, computer printout, ledger, etc. The once-processed papers contains various types of adhesives (pressure sensitive, hot melts, etc.), inks, and coating binders. An extensive list of natural and synthetic adhesives found in different grades of paper is described in the article, "Stickies Control by Detackification", Robert D. Moreland, 1986 Pulping Conference, pp. 193-196. This article also describes in some detail the problem solved by the present invention.
Different adhesive materials as well as pitch are present in paper fiber furnishes and a particular problem in paper recycling is the presence of adhesives, ink and coating binders (primarily those composed of synthetic polymers) that are found on some of the waste paper being utilized. More specifically, labels, decals, stickers, stamps, envelopes, book bindings, etc., each have adhesives associated therewith and these must be removed when the waste products are recycled. These adhesive contaminants, known in the trade as "stickies and tackies" cause numerous problems, both in terms of process and product performance. Some of the commonly used adhesive materials include, for example, styrene butadiene rubber, vinyl acrylate, polyvinyl alcohol, natural rubber, isoprene polystyrene, polypropylene, ethylene vinyl acetate and the like.
In papermaking, pitch is present in the form of a mixture of calcium carbonate, calcium soaps from wood components and other miscellaneous residues. A tacky, viscous substance, it is used extensively in the papermaking process and in the past has been extremely difficult to remove.
Specifically, the contaminants deposit on and adhere to machine surfaces throughout the paper processing machine thereby disrupting operations. They can fill or plug forming fabrics and press felts. The stickies will also mark or hole the paper sheet. If the contaminants are present in the paper, they will cause sheet defects or spots. This results in poor visual aesthetics of the paper, and poor surface properties can result in printing difficulties. The tackiness of these contaminants may also cause adjacent sheets, when wound in roll form, to adhere to one another. This can cause tears, breaks and holes in the converting processes.
Since stickies generally have the same density as water and fiber, they are difficult to remove. The stickies may be pliable and therefore cannot be completely screened from the water and/or fiber mixture. Equipment currently being utilized is effective to a certain degree but not 100%.
Obviously, production economics are affected quite severely when stickies-related problems are encountered. Stickies commonly necessitate complete shutdown of the manufacturing equipment in order to remove such by solvent washing techniques. The cleaning process is expensive due to downtime as well as solvent costs.
To deal with the problem of stickies and tackies, a number of strategies have been employed by papermakers. These strategies include mechanical and chemical means to either remove or passivate the contaminants.
Mechanical means of removing the contaminants include slotted pressure screens, hydrocyclones, and cleaners of various types. Also, thermal/mechanical dispersion units are employed to break the contaminants into micron sized particles, which are then difficult to detect in the final sheet. Despite these techniques, 100% removal of contaminants by mechanical means cannot be accomplished.
Chemically, several approaches are taken, including passivation or detackification of the sticky contaminant surfaces. Such detackification agents, include inorganic materials such as talc and zirconium compounds, organic materials such as polyvinyl alcohol, and hydrophobic synthetic fibers such as polypropylene. In addition, various dispersants may be used to prevent the contaminants from agglomerating. The small dispersed contaminants may be fixed to the paper sheet by the use of cationic polymers. Finally, if the contaminant problem becomes severe, solvents will be used to wash and remove the materials from the machine clothing.
The present invention relates to a method of detackifying secondary fiber paper pulps by treating the pulps with a hydrophobically modified guar and sodium acrylic-maleic acid copolymers.
U.S. Pat. No. 5,415,739 to Furman et al. discloses a process for the detackification of adhesive contaminants in secondary fiber paper pulps using a water soluble terphthalate glycol terpolymer. The terpolymer is prepared as the distillation product of polyethylene glycol monomers comprising at least 80% of the terpolymer; a phthalic ester moiety and a simple glycol such as ethylene glycol, propylene glycol and the like. The terpolymer is either added directly to the furnish prior to sheet formation or is sprayed on afterwards in the shower water used to clean off the fabrics and felts employed during sheet formation and dewatering.
U.S. Pat. No. 4,956,051 to Moreland discloses the use of a polyvinyl alcohol polymer to detackify adhesive materials contained in the secondary fibers of recycled waste papers. The polyvinyl alcohol polymer also contains some hydrophobic moieties such as acetate, propionate, butyrate and the like. The compound is added to the water sprays and showers used to wash the felts, wires and press rolls.
U.S. Pat. No. 4,886,575 also to Moreland discloses and claims a method for the detackification of hot melt and/or pressure sensitive adhesive materials contained in a fibrous paper sheet made from waste paper materials using a polyvinyl alcohol polymer that contains at least some hydrophobic groups such as acetate, propionate or butyrate, is 70-99% hydrolyzed and is water-soluble. The polymer is added to the water spray or shower for application to the paper sheets once pressed.
Finally, U.S. Pat. Nos. 4,781,794 and 4,698,133 also to Moreland disclose a method for the prevention of the deposition of adhesive materials contained in the waste paper materials used to make secondary paper products. The process entails the use of lower alkyl derivatives of cellulose in a dilute solution that is applied during the shower rinse of conventional secondary paper manufacturing production lines. Suitable derivatives include water soluble methyl ether derivatives such as methyl cellulose, hydroxypropyl methyl cellulose; hydroxybutyl methyl cellulose and the like. These are nonionic in nature and may also be used to spray the machine rollers and parts.
None of these prior art methods have been able to completely passivate the "stickies" and other contaminants which render the final paper product less than ideal and often times cause substantial defects and flows. It is an object of the present invention then, to provide a superior detackification process for use in the paper industry that prevents substantially all of the adhesive contaminant from depositing on and incorporating into the secondary paper products made from recycled waste materials or virgin pulp. The process is carried out using standard methods known in the art and yet provides a superior product at lower costs.

Acrylic acid/maleic acid copolymers as detackification agents for adhesives contained in secondary fiber