The present invention relates to an aqueous coating composition comprising: 5-95 wt. % of a polyurethane/acrylate hybrid dispersion and 95-5 wt. % of a dispersion of a polyurethane resin with oxidatively drying groups. Optionally, the coating composition comprises in addition to the above-mentioned dispersions an emulsion of an alkyd resin. The coating composition can be used as a translucent or opaque primer or topcoat or as a clearcoat in decorative applications.

This application is the national phase of International Patent Application No. PCT/EP99/08158, filed on Oct. 20, 1999, and which claims priority of European Patent Application No. 98203590.9, filed Oct. 26, 1998.
This invention relates to aqueous coating compositions and more particularly to aqueous coating compositions comprising a mixture of different polyurethane dispersions.
Aqueous coating compositions comprising a polyurethane dispersion are well-known for the production of film coatings on various substrates such as wood, metal, fabrics, and plastics. These may be useful for the provision of, for example, protective coatings, since polyurethane resins possess very desirable properties such as good chemical resistance, abrasion resistance, toughness, adhesion, and durability.
The present invention relates to an aqueous coating composition comprising: 5-95 wt. % of at least one polyurethane/acrylate hybrid dispersion and 95-5 wt. % of at least one dispersion of a polyurethane resin with oxidatively drying groups.
The weight percentages are based on the weight of total solid polyurethane resins present. The aqueous coating composition may comprise a mixture of different polyurethane/acrylate hybrid dispersions and/or a mixture of dispersions of different polyurethane resins with oxidatively drying groups.
It has been found that the use of a mixture of a polyurethane/acrylate hybrid dispersion and a dispersion of a polyurethane resin with oxidatively drying groups in aqueous coating compositions provides synergistic properties which cannot be obtained when using one of the polyurethane resin dispersions. Such properties are, for example, levelling, open time, and processability. Other properties such as scratch resistance and hardness remain at a very good level. Furthermore, coating compositions with a low VOC can be provided, as required by the present environmental laws.
In Tennebroek et al., European Coatings Journal, 1997, No. 11, pp. 1016-1021, an evaluation is provided of coating compositions comprising either a polyurethane/acrylate hybrid dispersion or a dispersion of a polyurethane resin with oxidatively drying groups. In Bell et al., Paint and Ink International, September/October 1996, pp. 6-10, an evaluation is provided of coating compositions comprising a dispersion of a polyurethane resin with oxidatively drying groups for application on wood surfaces. EP-A-0 332 326 discloses coating compositions comprising polyurethane/acrylate hybrid dispersions. None of the above-mentioned publications teaches or suggests the possibility of combining a polyurethane/acrylate hybrid dispersion with a dispersion of a polyurethane resin with oxidatively drying groups, nor are the synergistic effects obtained by this combination recognised.
Preferably, the aqueous coating composition comprises: 40-90 wt. % of at least one polyurethane/acrylate hybrid dispersion and 10-60 wt. % of at least one dispersion of a polyurethane resin with oxidatively drying groups.
The aqueous coating composition preferably has a VOC of 350 g/l or less, more preferably a VOC of 50 to 350 g/l, most preferably a VOC of 100 to 300 g/l, measured according to ASTM 3960-92.
A polyurethane/acrylate hybrid dispersion is defined as an aqueous dispersion comprising at least one polyurethane resin and at least one vinyl polymer. A vinyl polymer in this specification is meant to be a polymer obtained by the free radical addition polymerisation of at least one olefinically unsaturated monomer.
The polyurethane/acrylate hybrid dispersion may be formed by subjecting one or more vinyl monomers to free radical polymerisation conditions in the presence of a dispersion of an already chain-extended polyurethane resin using conventional techniques. Thus, free radical initiators may be added to a mixture of polyurethane dispersion and vinyl monomer or, alternatively, monomer may be added gradually to a polyurethane dispersion containing initiator.
In another variant of the preparation of polyurethane/acrylate hybrid dispersions a solution is formed of an isocyanate-terminated prepolymer in at least one vinyl monomer. The solution is then emulsified in an aqueous medium and the isocyanate-terminated prepolymer is chain extended. Subsequently, either vinyl monomer can be added and the polymerisation thereof initiated or the polymerisation of the vinyl monomer can be initiated and further vinyl monomer can be added during polymerisation.
Conventional free radical initiators may be used such as hydrogen peroxide, t-butyl hydroperoxide, persulphates such as NH4 persulphate, K persulphate, and Na persulphate. The amount generally is 0.05 to 3 wt. %, based on the weight of total vinyl monomers charged. Other suitable free radical initiators for such variants include mixtures such as a combination of t-butyl hydroperoxide, isoascorbic acid, and Fe.EDTA.
The weight ratio of polyurethane resin to vinyl resin in the composition is suitably in a range of 9:1 to 1:9, more preferably 5:1 to 1:5.
Preferably, the polyurethane/acrylate hybrid dispersion comprises hydrazine- (or hydrazone-) functional groups and carbonyl-functional groups to provide a self-crosslinking reaction. The hydrazine- (or hydrazone-) functional groups and carbonyl-functional groups may be present as chain pendant groups in the polyurethane or the polyacrylate or both, or they may be present as separate compounds in the polyurethane/acrylate hybrid dispersion. For the sake of clarity, in this specification (unless specified otherwise) by a carbonyl functionality is meant the carbonyl functionality of a ketone or aldehyde group. Also, by a hydrazine-functional group is meant the functional group of formula xe2x80x94NHNH2. A hydrazone-functional group is a group derived from such a hydrazine group by reaction with a monoketone or monoaldehyde containing at least 2 carbon atoms. It is preferred that the hydrazine- (or hydrazone-) functional groups and carbonyl-functional groups are present in an equivalent ratio of 1:20 to 20:1, more preferably 1:10 to 10:1.
As is well-known, polyurethane resins generally are made by reacting an organic polyisocyanate with an organic compound containing isocyanate-reactive groups, particularly a macro polyol, optionally with the inclusion of a low-molecular weight organic polyol. A favoured route to their formation involves the formation of an isocyanate-terminated polyurethane prepolymer followed by chain extension with an active hydrogen-containing compound.
The isocyanate-terminated prepolymer preparation reaction takes place under substantially anhydrous conditions at a temperature between about 30 and about 130xc2x0 C. until the reaction between the isocyanate groups and the isocyanate-reactive groups is substantially complete. During the production of the isocyanate-terminated prepolymer the reactants generally are used in proportions corresponding to a ratio of isocyanate groups to isocyanate-reactive groups of from about 1.1:1 to about 6:1, preferably from about 1.5:1 to 3:1. If desired, catalysts such as dibutyl tin dilaurate or stannous octoate may be used to assist prepolymer formation. A non-reactive organic solvent may optionally be added before or after prepolymer formation to control the viscosity. Suitable solvents which may be used include acetone, methylethyl ketone, dimethyl formamide, ethylene carbonate, propylene carbonate, diglyme, N-methyl pyrrolidone (NMP), ethyl acetate, ethylene and propylene glycol diacetates, alkyl ethers of ethylene and propylene glycol diacetates, alkyl ethers of ethylene and propylene glycol monoacetates, toluene, xylene, and sterically hindered alcohols such as t-butanol and diacetone alcohol. The preferred solvents are water-miscible solvents such as N-methyl pyrrolidone (NMP), dimethyl sulphoxide, and dialkyl ethers of glycol acetates or mixtures of N-methyl pyrrolidone (NMP) and methylethyl ketone.
The chain extension can be conducted at elevated, reduced or ambient temperatures. Convenient temperatures are from about 5 to 95xc2x0 C. or, more preferably, from about 10 to about 45xc2x0 C. The total amount of chain extender material(s) employed (besides water) should be approximately equivalent to the free-NCO groups in the prepolymer, the ratio of active hydrogens in the chain extender(s) to NCO groups in the prepolymer preferably being in the range from 0.7:1 to 2.0:1, more preferably 0.8:1 to 1.7:1. Of course, when water is employed as a chain extender, these ratios will not be applicable since the water, functioning both as chain extender and dispersing medium, will be present in a gross excess relative to the free-NCO groups.
The polyisocyanate used in making the isocyanate-terminated prepolymer may be an aliphatic, cycloaliphatic, araliphatic or aromatic polyisocyanate. Examples of suitable polyisocyanates include ethylene diisocyanate, 1,6-hexamethylene diisocyanate, isophorone diisocyanate, cyclohexane-1,4-diisocyanate, 4,4-dicyclohexylmethane diisocyanate, p-xylene diisocyanate, tetramethylxylene diisocyanate, 1,4-phenylene diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4-diphenylmethane diisocyanate, 2,4xe2x80x2-diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanates, and 1,5-naphthylene diisocyanate. Mixtures of polyisocyanates can be used and also polyisocyanates which have been modified by the introduction of urethane, allophanate, urea, biuret, carbodiimide, uretonimine, uretdione, or isocyanurate residues.
The polymeric organic compounds containing at least two isocyanate-reactive groups and having weight average molecular weights in the range 400-6000 which may be used in the preparation of isocyanate-terminated prepolymers preferably are polymeric organic polyols terminated by hydroxyl groups (although it would be possible to use polymeric compounds with other isocyanate-reactive groups, e.g., primary amino or carboxyl groups). The organic polyols particularly include diols and triols and mixtures thereof but higher functionality polyols may be used as minor components in admixture with diols. The polyols may be members of any of the chemical classes of polymeric polyols used or proposed for use in polyurethane formulations. In particular the polyols may be polyesters, polyester amides, polyethers, polythioethers, polycarbonates, polyacetals, polyolefins or polysiloxanes. Preferred polyol molecular weights are from 700 to 3000.
Polyester polyols which may be used include hydroxyl-terminated reaction products of polyalcohols such as ethylene glycol, propylene glycol, diethylene glycol, neopentyl glycol, butanediol, furan dimethanol, cyclohexane dimethanol, glycerol, trimethylol propane or pentaerythritol or mixtures thereof, with polycarboxylic acids, especially dicarboxylic acids or their ester-forming derivatives, for example heptanedioic acid, octanedioic acid, nonanedioic acid, decanedioic acid, succinic, glutaric and adipic acids or their dimethyl esters, phthalic anhydride or dimethyl terephthalate. Polyesters obtained by the polymerisation of lactones, for example caprolactone, in conjunction with a polyol, may also be used.
Polyester amides may be obtained by the inclusion of aminoalcohols such as ethanolamine in polyesterification mixtures.
Polyether polyols include products obtained by the polymerisation of a cyclic oxide, for example ethylene oxide, propylene oxide or tetrahydrofuran or by the addition of one or more such oxides to polyfunctional initiators, for example water, ethylene glycol, propylene glycol, diethylene glycol, cyclohexane dimethanol, glycerol, trimethylol propane, pentaerythritol or Bisphenol A. Especially useful polyethers include polyoxypropylene diols and triols, poly (oxyethyleneoxypropylene) diols and triols obtained by the simultaneous or sequential addition of ethylene and propylene oxides to appropriate initiators and poly-tetramethylene ether glycols obtained by the polymerisation of tetrahydrofuran. Amine-terminated polyether polyols may also be used.
Polythioether polyols which may be used include products obtained by condensing thiodiglycol either alone or with other glycols, dicarboxylic acids, formaldehyde, aminoalcohols or aminocarboxylic acids.
Polycarbonate polyols which may be used include products obtained by reacting diols such as 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol or tetraethylene glycol with diaryl carbonates, for example diphenyl carbonate, or with phosgene.
Suitable polyolefin polyols include hydroxy-terminated butadiene homo- and copolymers.
Organic polyols having molecular weights below 400 which may optionally be used in the preparation of isocyanate-terminated prepolymers particularly include diols and triols and mixtures thereof, but higher functionality polyols may be used. Examples of such lower-molecular weight polyols include ethylene glycol, diethylene glycol, tetraethylene glycol, bis(hydroxyethyl)terephthalate, cyclohexane dimethanol, furan dimethanol, glycerol, and the reaction products, up to a molecular weight of 399, of such polyols with propylene oxide and/or ethylene oxide.
Preferably, the isocyanate-terminated prepolymers are self-dispersible in water. This may be achieved by including isocyanate-reactive and/or diisocyanate compound(s) bearing non-ionic and/or ionic dispersing groups (or groups which may subsequently be converted to such dispersing groups) as reactants In the preparation of the prepolymer.
Typically, ionic dispersing groups are anionic salt groups, e.g., carboxylate salt groups. Such groups may be provided, e.g., by employing an isocyanate-reactive compound having at least one acid group and at least two hydroxyl groups as a reactant in the prepolymer formation. The preferred carboxy-containing diol is 2,2-dimethylolpropionic acid. If desired, the carboxy containing diol or triol may be incorporated into a polyester by reaction with a dicarboxylic acid before being incorporated into the prepolymer.
The conversion of any acid groups present in the prepolymer to anionic salt groups may be effected by neutralising the acidic groups before, after (if in combination with non-ionic stabilisation) or simultaneously with the formation of an aqueous dispersion of the prepolymer.
Non-ionic dispersing groups typically are pendant polyoxyalkylene groups, particularly polyoxyethylene groups. Such groups may be provided, e.g., by employing diols having pendant polyoxyethylene chains as a reactant in the prepolymer formation. The polyethylene glycol monoethers suitably have weight average molecular weights in the range of 250 to 3000 and, preferably, in the range of 500 to 2000. If desired, the polyoxyethylene chains may contain units of other alkylene oxides in addition to the ethylene oxide units. Thus, polyoxyalkylene chains in which up to 60% of the alkylene oxide units are propylene oxide units, the remainder being ethylene oxide units, may be used.
The pendant dispersing group content of the polyurethane resin (if present) may vary within wide limits but should be sufficient to provide the polyurethane resin with the required degree of water dispersibility. Typically, the pendant dispersing group content will vary from 10 to 90 milli-equivalents (more preferably from 18 to 65 milli-equivalents) of pendant anionic dispersing groups (particularly carboxylate groups) per 100 g polyurethane resin and/or from 0.5 to 250 milli-equivalents of pendant (lateral or terminal) non-ionic dispersing groups (particularly polyethylene oxide groups) per 100 g polyurethane resin.
The aqueous polyurethane dispersions may be prepared by dispersing the isocyanate-terminated polyurethane prepolymer (optionally carried in an organic solvent medium) in an aqueous medium (using, e.g., surfactants or, more preferably, by utilising the self-dispersibility of the prepolymer if dispersing groups are present therein. although surfactants may still be employed if desired) and chain extending the prepolymer with an active hydrogen-containing chain extender in the aqueous phase. The prepolymer may also be chain extended to form the polyurethane resin while dissolved in organic solvent (usually acetone), followed by the addition of water to the polymer solution until water becomes the continuous phase and the subsequent removal of the solvent by distillation to form a purely aqueous dispersion. Active hydrogen-containing chain extenders include a polyol, an amino-alcohol, a primary or secondary aliphatic, alicyclic, aromatic, araliphatic or heterocyclic diamine or polyamine, or hydrazine or a substituted hydrazine. Water-soluble chain extenders are preferred and water itself may be effective. Examples of such chain extenders useful herein include ethylene diamine, diethylene triamine, triethylene tetramine, propylene diamine, butylene diamine, hexamethylene diamine, cyclohexylene diamine, piperazine, 2-methyl piperazine, phenylene diamine, tolylene diamine, xylylene diamine, tris(2-aminoethyl)amine, 3,3xe2x80x2-dinitrobenzidine, 4,4xe2x80x2-diaminodiphenyl methane, menthane diamine, m-xylene diamine, isophorone diamine, and adducts of diethylene triamine to acrylate or its hydrolysed products. Other chain extenders include hydrazine, azines such as acetone azine, substituted hydrazines such as dimethyl hydrazine, 1,6-hexamethylene-bis-hydrazine, carbodihydrazine, hydrazides of dicarboxylic acids and sulfonic acids such as adipic acid mono- or dihydrazide, oxalic acid dihydrazide, isophthalic acid dihydrazide, hydrazides made by reacting lactones with hydrazine such as gamma-hydroxylbutyric hydrazide, bis-semi-carbazide, and bis-hydrazide carbonic esters of glycols such as any of the glycols mentioned above. Where the chain extender is other than water, for example a polyol, polyamine or hydrazine, it may be added to the aqueous dispersion of prepolymer or, alternatively, it may already be present in the aqueous medium when the prepolymer is dispersed therein.
Carbonyl functionality may be introduced into the polyurethane backbone during the prepolymer formation and/or during the chain extension step. The carbonyl functionality in the polyurethane resin may be incorporated by virtue of (an) isocyanate-reactive compound(s) providing carbonyl functionality being included as a reactant in the formation of the isocyanate terminated prepolymer. Examples of such compounds are carbonyl compounds with at least one and preferably at least two isocyanate-reactive groups, e.g., dihydroxyketones such as dihydroxyacetone and the adduct obtained by a Michael addition reaction of diacetone acrylamide with a diamine or an alkanolamine. Carbonyl compounds with only one isocyanate-reactive group can also be used if the urethane chain has been compensatingly branched with, e.g., triols, triisocyanates and/or triamines.
Otherwise, the active hydrogen-containing chain extending material may include a proportion of or be entirely composed of extending material providing carbonyl functionality. Examples include carbonyl-functional diamino compounds such as the Michael addition product of two moles of di-acetone acrylamide with one mole of a diamine.
Hydrazine (or hydrazone) functionality may be introduced during the prepolymer formation and/or during the chain extension step. The hydrazine (or hydrazone) functionality in the polyurethane resin may be incorporated by virtue of (an) isocyanate-reactive compound(s) providing hydrazine (or hydrazone) functionality pendant to the polyurethane chain being included as a reactant in the formation of the isocyanate-terminated prepolymer. Examples include a monoaldehyde- or monoketone-blocked hydrazine compound, by which is meant a compound in which the hydrazine functionality has been blocked by reaction with a monoaldehyde or a monoketone (preferably of boiling point 30-200xc2x0 C., such as acetone or methylethyl ketone) to form a hydrazone structure. This expedient is employed because otherwise a hydrazine functionality will react during the prepolymer preparation and so be partially or even completely removed. The blocked hydrazine functionality is not labile under anhydrous conditions, however, and moreover is sufficiently stable at pH above 7 (preferably above 8) even in an aqueous medium, such alkaline conditions preferably being achieved by the presence of a volatile organic amine such as triethylamine. Consequently, the chain extension step may be performed with the prepolymer in aqueous dispersion and the chain extending agent(s) in the aqueous phase, with the pH above 7 (preferably above 8), without the blocked hydrazine functionality being significantly affected or removed. Subsequent acidification as a result of evaporation of the neutralising agent during film formation will cause regeneration of the hydrazine functionality (which is then available for crosslinking purposes) together with the monoaldehyde or monoketone blocking compound (which, if a volatile material such as acetone or methylethyl ketone is used, will also be removed by evaporation during film formation).
Active hydrogen-containing chain extending compounds with a hydrazine (or hydrazone) functionality include diamino hydrazides. Such compounds may be prepared by reacting a diamine of formula H2Nxe2x80x94R1xe2x80x94NH2 with 0.2 to 2 moles of an acrylic acid derivative, preferably ethyl acrylate, and then reacting the product obtained with hydrazine. Suitable diamines of the formula H2Nxe2x80x94R1xe2x80x94NH2 include aliphatic diamines with 2 to 15 carbon atoms and cycloaliphatic and aromatic diamines with 6 to 15 carbon atoms such as ethylene diamine, 1,4-butane diamine, 1,6-hexane diamine, 2-methyl-1,5-pentane diamine, 2,2,4-trimethyl-1,6-hexane diamine, 2,2,4- and 2,4,4-trimethyl-1,6-hexane diamine, isophorone diamine, bis(4-aminocyclohexyl)methane, and di(aminomethyl)benzene. Isophorone diamine is a preferred diamine.
Polyurethane resins which incorporate chain-pendant carbonyl functionality preferably contain a proportion of carbonyl groups in the resin within the range of 3 to 140 milli-equivalents, more preferably 5 to 80 milli-equivalents, per 100 g of polyurethane resin. Polyurethane resins which incorporate chain-pendant hydrazide (or hydrazone) functionality in the resin preferably contain a proportion within the range of 3 to 140 milli-equivalents, more preferably 6 to 80 milli-equivalents, per 100 g of polyurethane resin. The polyurethane/acrylate hybrid dispersions may also incorporate polycarbonyl compound(s). Examples of suitable polycarbonyl compounds are di- or poly-ketones, di- or poly-aldehydes, and aidehyde-ketones such as glyoxal, 2,5-hexanedione, glutaric dialdehyde, succinic dialdehyde, acetyl acetone, acetonyl acetone, and acetone dicarboxylic acid ester.
Examples of such suitable polyhydrazine (or polyhydrazone) compounds include dicarboxylic acid bishydrazides such as oxalic acid dihydrazide, maleic acid dihydrazide, succinic acid dihydrazide, glutaric acid dihydrazide, adipic acid dihydrazide, cyclohexane dicarboxylic acid bis-hydrazide, azelaic acid bis-hydrazide, and sebacic acid dihydrazide. Other suitable compounds are polyhydrazides of carbonic acid, e.g., carbonic acid dihydrazide, and bis-semicarbazides, especially aliphatic and cycloaliphatic bis-semicarbazides. Polyhydrazides of aromatic polycarboxylic acids, e.g., the dihydrazides of phthalic acid, terephthalic acid and isophthalic acid, and the dihydrazides, trihydrazides, and tetrahydrazides of pyromellitic acid, are other examples. Examples of other suitable compounds are trihydrazides, e.g., nitrilotriacetic acid trihydrazide, and tetrahydrazides, e.g., ethylene diamine tetraacetic acid tetrahydrazide. The compositions of the invention may optionally contain 0.0002 to 0.02 mole per mole of hydrazine (or hydrazone) groups of a heavy metal ion. This may be added in the form of suitable water-soluble metal salts, particularly chlorides, sulphates, and acetates. Suitable heavy metal water-soluble salts are, in particular, those of Cu, Zn, Fe, Cr, Mn, Pb, V, Co, and Ni.
The vinyl polymer is obtained by the free radical addition polymerisation of at least one olefinically unsaturated monomer selected from esters of acrylic acid and methacrylic acid, examples of which are methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-butyl acrylate, n-butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, isopropyl acrylate, isopropyl methacrylate, n-propyl acrylate, and n-propyl methacrylate. The vinyl polymer may be obtained by introducing other vinyl monomers such as 1,3-butadiene, isoprene, styrene, divinyl benzene, acrylonitrile, methacrylonitrile, vinyl halides (such as vinyl chloride), vinyl esters (such as vinyl acetate, vinyl propionate, and vinyl laurate), heterocyclic vinyl compounds, alkyl esters of monolefinically unsaturated dicarboxylic acids (such as di-n-butyl maleate and di-n-butyl fumarate). In addition, the vinyl polymer may contain, as copolymerised units, small amounts (mostly from 0.5 to 10% by weight) of monoolefinically unsaturated monocarboxylic acids and/or dicarboxylic acids, mostly of 3 to 6 carbon atoms, and/or of their N-unsubstituted or N-substituted amides, especially acrylic acid, methacrylic acid, beta-carboxyethylacrylate, fumaric acid, itaconic acid, acrylamide, methacrylamide, N-methyl acrylamide, N-methylol acrylamide, N-n-butoxymethyl methacrylamide, maleimide, and maleic acid diamide, as well as monoolefinically unsaturated sulphonic acids, especially vinyl sulphonic acid and methacrylamidopropane sulphonic acid.
Examples of carbonyl-containing vinyl monomers which may be mentioned include acrolein, methacrolein, diacetone-acrylamide, crotonaldehyde, 4-vinylbenzaldehyde, vinyl alkyl ketones with 4 to 7 carbon atoms such as vinyl methyl ketone, and acryloxy- and methacryloxy-alkyl propanals. Further examples include acrylamidopivalaldehyde, methacrylamidopivalaldehyde, 3-acrylamidomethyl anisaldehyde, diacetone acrylate, acetonyl acrylate, diacetone methacrylate, acetoacetoxyethyl methacrylate, 2-hydroxypropyl acrylate acetylacetate, and butanediol acrylate acetylacetate. The proportion of carbonyl-functional groups in the vinyl polymer preferably is 3 to 200 milli-equivalents per 100 g polymer (more preferably 8 to 100 milli-equivalents per 100 g polymer). Preferably a vinyl polymer bearing chain-pendant hydrazine- (or hydrazone-) functional groups is the product formed by reacting at least a free radical addition polymer formed by polymerising at least one olefinically unsaturated monomer providing chain-pendant hydrazinolysable groups and a hydrazine-yielding agent, whereby at least a proportion of the chain-pendant hydrazinolysable groups are converted to hydrazine-functional groups. Suitable groups for hydrazinolysis are, e.g., acid, acid halide and (especially) ester groups. Examples of monomers providing chain-pendant hydrazinolysable groups include crotonic acid, xcex1-chloracrylic acid, and especially acrylic acid, and acid chlorides or esters thereof, and also methacrylic acid and acid chlorides or esters thereof. Advantageously use is made of acrylic acid esters of alcohols of low molecular weight, such as methyl, ethyl, propyl, isopropyl, n-butyl or secondary butyl esters.
As hydrazine agents may be particularly mentioned hydrazine itself and hydrazine monohydrate. When a hydrazone-containing vinyl polymer is required, the hydrazine groups may be converted to hydrazone groups by reacting a saturated monoketone or monoaldehyde containing at least two carbon atoms and, preferably, having a boiling point of 30 to 200xc2x0 C. Examples of such compounds include, for example, aliphatic ketones or aldehydes, such as acetone, ethylmethyl ketone, diisopropyl ketone, isobutylmethyl ketone, di-n-butyl ketone, dodecylmethyl ketone, octadecyl isobutyl ketone. acetaldehyde or propionaldehyde, or cycloalipatic ketones such as cyclohexanone, or camphor, or aryl alkyl ketones, such as acetophenone, or compounds such as benzaldehyde or furturaldehyde, or finally amino-ketones or amino-aldehydes, such as para-acetylamino-benzaldehyde, diacetone-amine, N-methyl-diacetone-amine, aminomethylphenyl ketone, or oxy-ketones and oxy-aldehydes, such as glucose, fructose, ortho-oxyacetophenone, salicylaldehyde or halogenated aldehydes and ketones such as chloral or chlorinated acetones.
Examples of polyurethane/acrylate hybrid dispersions include Neopac E125 and Neopac E121, ex Zeneca, Hybridur HY 570 and HY 540, ex Air products, and Daotan VTW 1265, ex Vianova.
Polyurethane dispersions with oxidatively drying groups may be prepared as mentioned above by the reaction of an organic polyisocyanate with an organic compound containing isocyanate-reactive groups, particularly a macro polyol, optionally with the inclusion of a low-molecular weight organic polyol. A favoured route to their formation involves the formation of an isocyanate-terminated polyurethane prepolymer followed by chain extension with an active hydrogen-containing compound. Such a reaction route is described in EP-A-0 444 454.
To introduce oxidative groups into such a polyurethane resin, the polyols mentioned above may be prepared by the reaction of a hydroxyl-, carboxyl-, amino-, and thiol-reactive compound comprising oxidative groups. Such oxidative groups are derivatives of (poly)unsaturated fatty acids, preferably those containing 12 to 26 carbon atoms. Specific examples are mono-unsaturated fatty acids, such as lauroleic acid, myristoleic acid, palmitoleic acid, oleic acid, gadoleic acid, erucic acid, ricinolinic acid; bi-unsaturated fatty acids, such as linoleic acid; tri-unsaturated acids, such as linolenic acid, eleostearic acid, and licanic acid; quadri-unsaturated fatty acids, such as arachidonic acid and clupanodonic acid, and other unsaturated fatty acids obtained from animal or vegetable oils. The polyurethane dispersion may further comprise derivatives of saturated fatty acids, such as lauric acid, myristic acid, palmitic acid, stearic acid, and arachidic acid.
Examples of polyurethane dispersions with oxidatively drying groups include Neorez R2001, Neorez R2020, and Neorez R2040, ex Zeneca, Valires HA 04001, ex Actichem, Spensol F97 ex Reichold, and Halwedrol OX 47-1-40, ex Hxc3xcttenes-Albertus.
Optionally, other resins may be present in the coating composition according to the present invention. Examples of these resins include polyurethane resins, polyacrylate resins, and alkyd resins. Preferably, an alkyd resin is added to the coating composition. Preferably, the coating composition comprises 10 to 70 wt. % alkyd resin on total solid resins. More preferably, the coating composition comprises 25 to 60 wt. % alkyd resin on total solid resins.
At least part of the alkyd resin comprises oxidatively drying groups, i.e., unsaturated, aliphatic compounds, at least a portion of which is polyunsaturated. Thus, the alkyd resin may be prepared from unsaturated and saturated fatty acids, polycarboxylic acids, and di- or polyvalent hydroxyl compounds.
The number of unsaturated fatty acids eligible for use in the preparation of the alkyd resins to be employed according to the invention is exceedingly large. However, preference is given to the use of mono- and polyunsaturated fatty acids, preferably those containing 12 to 26 carbon atoms. Specific examples are mono-unsaturated fatty acids, such as lauroleic acid, myristoleic acid, palmitoleic acid, oleic acid, gadoleic acid, erucic acid, ricinolinic acid; bi-unsaturated fatty acids, such as linoleic acid; tri-unsaturated acids, such as linolenic acid, eleostearic acid, and licanic acid; quadri-unsaturated fatty acids, such as arachidonic acid and clupanodonic acid, and other unsaturated fatty acids obtained from animal or vegetable oils. The number of saturated fatty acids is also exceedingly large. Preference is given to the use of saturated fatty acids containing 12 to 26 carbon atoms. Specific examples include lauric acid, myristic acid, palmitic acid, stearic acid, and arachidic acid. Other monocarboxylic acids suitable for use include tetrahydrobenzoic acid and hydrogenated or non-hydrogenated abietic acid or its isomer. If so desired, the monocarboxylic acids in question may be used wholly or in part as triglyceride, e.g., as vegetable oil, in the preparation of the alkyd resin. If so desired, mixtures of two or more of such monocarboxylic acids or triglycerides may be employed, optionally in the presence of one or more saturated, (cyclo)aliphatic or aromatic monocarboxylic acids, e.g., pivalic acid, 2-ethylhexanoic acid, lauric acid, palmitic acid, stearic acid, 4-tert.butyl-benzoic acid, cyclopentane carboxylic acid, naphthenic acid, cyclohexane carboxylic acid, 2,4-dimethyl benzoic acid, 2-methyl benzoic acid, and benzoic acid.
Examples of polycarboxylic acids include phthalic acid, isophthalic acid, terephthalic acid, 5-tert. butyl isophthalic acid, trimellitic acid, pyromellitic acid, succinic acid, adipic acid, 2,2,4-trimethyl adipic acid, azelaic acid, sebacic acid, dimerised fatty acids, cyclopentane-1,2-dicarboxylic acid, cyclohexane-1,2-dicarboxylic acid, 4-methylcyclohexane-1,2-dicarboxylic acid, tetrahydrophthalic acid, endomethylene-cyclohexane-1,2-dicarboxylic acid, butane-1,2,3,4-tetracarboxylic acid, endoisopropylidene-cyclohexane-1,2-dicarboxylic acid, cyclohexane-1,2,4,5-tetracarboxylic acid, and butane-1,2,3,4-tetracarboxylic acid. If so desired, the carboxylic acids in question may be used as anhydrides or in the form of an ester, e.g., an ester of an alcohol having 1-4 carbon atoms.
In addition, the alkyd resin comprises di- or polyvalent hydroxyl compounds. Examples of suitable divalent hydroxyl compounds are ethylene glycol, 1,3-propane diol, 1,6-hexane diol, 1,12-dodecane diol, 3-methyl-1,5-pentane diol, 2,2,4-trimethyl-1,6-hexane diol, 2,2-dimethyl-1,3-propane diol, and 2-methyl-2-cyclohexyl-1,3-propane diol. Examples of suitable triols are glycerol, trimethylol ethane, and trimethylol propane. Suitable polyols having more than 3 hydroxyl groups are pentaerythritol, sorbitol, and etherification products of the compounds in question, such as ditrimethylol propane and di-, tri-, and tetrapentaerythritol. Preferably, use is made of compounds having 3-12 carbon atoms, e.g., trimethylol propane and pentaerythritol.
The alkyd resins can be obtained by direct esterification of the constituent components, with the option of a portion of these components having been converted already into ester diols or polyester diols. Alternatively, the unsaturated fatty acids can be added in the form of a drying oil, such as sunflower oil, linseed oil, tuna fish oil, dehydrated castor oil, coconut oil, and dehydrated coconut oil. Transesterification with the other added acids and diols will then give the final alkyd resin. This transesterification generally takes place at a temperature in the range of 115 to 250xc2x0 C., optionally with solvents such as toluene and/or xylene also present. The reaction generally is carried out in the presence of a catalytic amount of a transesterification catalyst. Examples of transesterification catalysts suitable for use include acids such as p-toluene sulphonic acid, a basic compound such as an amine, or compounds such as calcium oxide, zinc oxide, tetraisopropyl orthotitanate, dibutyl tin oxide, and triphenyl benzyl phosphonium chloride.
The number average molecular weight of the alkyd resin thus prepared preferably is at least 1000, preferably from 2000 to 5000. To be incorporated into the coating composition of the present invention, the alkyd resin is dispersed in water with 2-30 wt. % surfactant.
For the purposes of this invention an aqueous coating composition means a composition in an aqueous medium of which water is the principal component. Minor amounts of organic liquids, i.e. co-solvents may optionally be present. Examples of co-solvents include propylene carbonate, N-methyl pyrrolidone (NMP), ethylene diglycol, butyl glycol, butyl diglycol, n-butoxy propanol, and dipropylene glycol monomethyl ether.
If so desired, the coating composition according to the invention may contain all sorts of additives or adjuvants, e.g., pigments, dyes, fillers, anti-oxidants, anti-ozonants, matting agents, thixotropic agents, pigment dispersing agents, thickening agents, wetting agents, siccatives sterically hindered amines, bactericides, fungicides, anti-skinning agents, perfumes, anti-foaming agents, drying stabilisers, and waxes. Preferably, a thickening agent is used in the coating composition of the present invention, such as Acrysol RM5, ex Rohm and Haas, and Polyphobe 9823, ex Union Carbide. More preferably, such a thickening agent is an associative thickener, such as associative polyurethane and polyacrylate thickeners. Examples include Acrysol RM 2020 and Acrysol RM8, ex Rohm and Haas, Bermodol PUR2130, ex Akzo Nobel, Rheo 2000 and Coapur 5035, ex Coatex, Tafigel PUR 40 and Tafigel PUR 45, ex Muntzing, Serad FX 1035 and FX 1070, ex Servo, and Optiflo L100 and L120, ex Ashland Sxc3xcd-chemie. Preferably, up to 10 wt. % (solid on solid resin) of thickening agent is used in the present coating compositions, more preferably 1 to 10 wt. %, most preferably 2 to 5 wt. %.
Siccatives may also be present in the coating compositions of the invention. Examples of siccatives are metal salts of aliphatic acids including cycloaliphatic acids, such as octanoic acid and naphthenic acid, where the metal is, for example, cobalt, manganese, lead, zirconium, calcium, zinc, and rare earth metals. Also mixtures of siccatives are used. The siccatives (calculated as
Unless otherwise stated, the properties of the coating compositions and the resulting films are measured as follows.
The coating compositions were applied on glass panels with a draw bar (150 xcexcm theoretical wet film thickness) by using the K control coater for a reproducible application rate method. The films were aged at 23xc2x0 C. for 4 weeks. The Kxc3x6nig Hardness was measured in number of oscillations at several time intervals during ageing in accordance with ISO 1522.
The coating composition was applied with a brush on a tin panel (12 m2/l). After one day drying at room temperature, a second layer was applied to half of the panel. Levelling on both halves of the panel was determined by assessing the brush marks on a scale from 1(=bad) to 10 (=good). Recoatability was also assessed on the same scale.
The xe2x80x9cpracticalxe2x80x9d open time was determined by applying 80 g/m2 of a coating composition on a plastified hardboard panel and rebrushing a small strip every minute. The panel was dried overnight at room temperature. The open time is the time (in minutes) after which the brushmarks of the rebrushing remain visible in the dried paint.
The wet edge time was determined by applying 80 g/m2 of a coating composition on the first half of a plastified hardboard panel. At 1 minute intervals narrow stripes were applied on the second half of the panel, partly overlapping the painted first half of the panel. The panel was dried overnight at metal) are usually applied in an amount of 0,001 to 5 wt. %, calculated on the alkyd resin solids content.
Suitable pigments are, e.g., natural or synthetic pigments which may be transparent or not. Examples of suitable pigments are titanium dioxide, red iron oxide, orange iron oxide, yellow iron oxide, phthalocyanine blue, phthalocyanine green, molybdate red, chromium titanate, and earth colours such as ochres, green earths, umbers, and burnt or raw Siennas.
The coating compositions can be applied to a substrate in any suitable manner, e.g., by means of roller coating, spraying, brushing, sprinkling, flow coating or dipping. Preferably, the composition is applied by brushing and roller coating.
Suitable substrates include metals or synthetic materials, wood, concrete, cement, brick, paper or leather, all of which may optionally have been pre-treated or pre-painted. Suitable metals include iron, steel, and aluminium. The applied coat can be cured very suitably at a temperature of, e.g., 0-40xc2x0 C. Optionally, a curing temperature above 40xc2x0 C. may be employed, as a result of which the curing time can be reduced. Preferably, the coating composition can be used as translucent or opaque primer or topcoat or as clearcoat in decorative applications.

Aqueous coating composition comprising a mixture of polyurethane dispersions


The present invention is a hot melt pressure sensitive positioning adhesive for use with an absorbent article. The adhesive comprises:

This invention relates to hot melt pressure sensitive positioning adhesives for use with absorbent articles which are based on hydrogenated block copolymers of styrene and butadiene or isoprene and exhibit improved viscosity and viscosity/temperature profile.
Positioning adhesives are used on disposable articles (absorbent articles) such as sanitary napkins, incontinent pads, bed pads, feminine pads, panty shields, and diaper inserts, where an adhesive layer is used to attach the article to a woven fabric substrate such as a supporting undergarment or bed sheet. The positioning adhesive is commonly applied to a release liner and transfer coated to the garment facing surface of the disposable article. The positioning adhesive must be capable of attaching to the undergarment to hold the article in place without transferring to or otherwise being deposited on the undergarment. Furthermore, the adhesive must not discolor, damage, or disturb the fibers of the garment.
The positioning adhesive must be a pressure sensitive adhesive that has an application viscosity that permits it to readily flow onto and partially penetrate the particular surface to which it is applied. It must have good bond strength and high tack for initial placement of the article on the undergarment but also must have the ability to avoid loss of adhesion over time due to temperature conditions. Finally, these articles are sometimes used for long periods of times at body temperature and they can have the drawback that the hot melt adhesive gradually softens and penetrates into the undergarment to which the article is adhering. In this case, the adhesive force greatly increases and the cohesive force is reduced. This causes the adhesive layer to suffer cohesion breakdown when the article is removed and some adhesive remains on the undergarment. Prevention of this deposit of adhesive on the undergarment is accordingly a necessary prerequisite for a successful positionable hot melt adhesive composition.
Block copolymers of styrene and dienes such as butadiene or isoprene have been used for a number of years in positionable hot melt adhesive formulations. More recently, the material of choice for such adhesives in feminine care applications has been hydrogenated block copolymers of styrene and butadiene such as KRATON(copyright) G1650 SEBS hydrogenated styrene-butadiene-styrene) block copolymer. These SEBS block copolymers that have been used in this application (see U.S. Pat. No. 5,777,031) generally have a vinyl content of 18 to 50% by weight. KRATON G1650 has a vinyl content of about 35% by weight. Formulations based on these SEBS block copolymers have been found to have excellent adhesion to fabrics like cotton and nylon and have the advantage that they leave no residue after peeling. The application viscosity i.e. melt viscosity, of formulations using these polymers is acceptable but it would be advantageous to have a positionable adhesive formulation which has a lower melt viscosity in order to be able to lower the application temperature. This reduces the risk of degradation, char forming, and filter plugging. This also results in energy and cost savings, decreases maintenance costs, and reduces the amount of odor due to any volatiles coming from the adhesive formulation. The present invention provides such an improved positionable hot melt adhesive formulation.
The present invention is a hot melt pressure sensitive positioning adhesive for use with an absorbent article. The adhesive comprises:
(a) from greater than 6 to less than 15 percent by weight of the total of (a), (b) and (c) of a hydrogenated styrene-(butadiene and/or isoprene)-styrene block copolymer having a vinyl content of from greater than 50 to 90%, preferably 70 to 80% by weight of the total butadiene and/or isoprene block; and
(b) from 50 to 80 percent by weight of the total of (a), (b) and (c) of a tackifying resin which has an aromaticity such that the MMAP is at least 45xc2x0 C.; and
(c) from 5 to 35 percent by weight of the total of (a), (b), and (c) of a plasticizer.
The term xe2x80x9cvinyl contentxe2x80x9d refers to the fact that a conjugated diene may be polymerized via 1,2-addition (in the case of butadienexe2x80x94it would be 3,4-addition or 1,2-addition in the case of isoprene). Although a pure xe2x80x9cvinylxe2x80x9d group is formed only in the case of 1,2-addition polymerization of 1,3-butadiene, the effects of 3,4-addition polymerization of isoprene (and similar addition for other conjugated dienes) on the final properties of the block copolymer will be similar. The term xe2x80x9cvinylxe2x80x9d refers to the presence of a pendant vinyl group on the polymer chain. The purpose here is to introduce chain branching and to reduce the size of the main polymer backbone (since some of the carbons in the diene are in the pendant group) which reduces the end to end length of the molecule and, in turn, its viscosity in the cement.
One of the primary components of the positioning adhesive composition of the present invention is the above-described hydrogenated block copolymer which has two polystyrene endblocks and a saturated or hydrogenated polybutadiene and/or polyisoprene midblock. This hydrogenated base block copolymer provides the primary load bearing capability of the adhesive composition. It is important that the polymer be hydrogenated so that the structural integrity of the polymer is preserved even if outside forces that cause degradation are encountered. The block copolymer may be hydrogenated as generally described in the prior art, preferably so as to reduce at least 90 percent of any olefinic double bonds in the polymer chains. Suitably at least 50 percent, preferably at least 70 percent, and more preferably at least 90 percent, most preferably at least 95 percent of the original olefinic unsaturation is hydrogenated.
Polymerisation of butadiene (and/or isoprene) must produce a polymer block with a high vinyl content. This typically involves anionic polymerisation in an apolar solvent in the presence of a structure modifier, as is well known in the art. The vinyl content should be greater than 50% by weight, preferably 50-90%, more preferably 70 to 80%wt. At 50% or below, the polymer viscosity is similar to conventional polymers and there is no advantage. Above 90%wt, the viscosity decrease has reached a plateau and no longer drops with higher vinyl content. Therefore, there is no further advantage.
Anionic polymerization of conjugated diene hydrocarbons with lithium initiators is well known as described in U.S. Pat. Nos. 4,039,593 and Re. 27,145 which descriptions are incorporated herein by reference. Polymerization commences with a monolithium, dilithium, or polylithium initiator which builds a living polymer backbone at each lithium site. Typical living polymer structures containing polymerized conjugated diene hydrocarbons are:
Xxe2x80x94Bxe2x80x94Li
Xxe2x80x94Axe2x80x94Bxe2x80x94Li
Xxe2x80x94Axe2x80x94Bxe2x80x94Axe2x80x94Li
Lixe2x80x94Bxe2x80x94Yxe2x80x94Bxe2x80x94Li
Lixe2x80x94Axe2x80x94Bxe2x80x94Yxe2x80x94Bxe2x80x94Axe2x80x94Li
wherein B represents polymerized units of one or more conjugated diene hydrocarbons such as butadiene or isoprene, A represents polymerized units of one or more vinyl aromatic compounds such as styrene, X is the residue of a monolithium initiator such as sec-butyllithium, and Y is the residue of a dilithium initiator such as the diadduct of sec-butyllithium and m-diisopropenylbenzene. Some structures, including those pertaining to polylithium initiators or random units of styrene and a conjugated diene, generally have limited practical utility although known in the art.
The anionic polymerization of the conjugated diene hydrocarbons is typically controlled with structure modifiers such as diethylether or ethyl glyme (1,2-diethoxyethane) to obtain the desired amount of 1,2-addition. (i.e. vinyl content). A 1,2-addition of about 40% may be achieved during polymerization at 50xc2x0 C. with about 6% by volume of diethylether or about 200 ppm of ethyl glyme in the final solution. A 1,2 addition of about 47% may be achieved during polymerization by the presence of about 250 ppm of ortho-dimethoxybenzene (ODMB) in the final solution. A 1,2 addition of 78% may be achieved during polymerization by the presence of about 300 ppm of 1,2-diethoxypropane (DEP) in the final solution.
In general, the polymers useful in this invention may be prepared by contacting the monomer or monomers with an organoalkali metal compound in a suitable solvent, typically in the presence of a structure modifier, at a temperature in the range from xe2x88x92150xc2x0 C. to 300xc2x0 C., preferably at a temperature within the range from 0xc2x0 C. to 100xc2x0 C. Particularly effective polymerization initiators are organolithium compounds having the general formula:
RLi
wherein R is an aliphatic, cycloaliphatic, alkyl-substituted cycloaliphatic, aromatic or alkyl-substituted aromatic hydrocarbon radical having from 1 to 20 carbon atoms.
Suitable solvents include those useful in the solution polymerization of the polymer and include aliphatic, cycloaliphatic, alkyl-substituted cyclo-aliphatic, aromatic and alkyl-substituted aromatic hydrocarbons, ethers and mixtures thereof. Suitable solvents, then, include aliphatic hydrocarbons such as butane, pentane, hexane, and heptane, cycloaliphatic hydrocarbons such as cyclohexane and cycloheptane, alkyl-substituted cycloaliphatic hydrocarbons such as methylcyclohexane and methylcycloheptane, aromatic hydrocarbons such as benzene and the alkyl-substituted aromatic hydrocarbons such as toluene and xylene, and ethers such as tetrahydrofuran, diethylether, and di-n-butyl ether.
When polar solvents like tetrahydrofuran are used, structure modifiers are typically not necessary for the preparation of high vinyl content butadiene and/or isoprene polymer blocks.
The hydrogenation of these polymers may be carried out by a variety of well established processes including hydrogenation in the presence of nickel catalysts such as Raney Nickel, noble metal catalysts such as those containing platinum, and/or palladium and soluble transition metal catalysts. Suitable hydrogenation processes which can be used are ones wherein the diene-containing polymer or copolymer is dissolved in an inert hydrocarbon diluent such as cyclohexane and hydrogenated by reaction with hydrogen in the present of a soluble hydrogenation catalyst. Such processes are disclosed in U.S. Pat. Nos. 3,113,986, 4,226,952 and Reissue 27,145, the disclosures of which are herein incorporated by reference. The polymers are preferably hydrogenated in such a manner as to produce hydrogenated polymers having a residual unsaturation content in polydiene blocks of less than about 1 percent, and most preferably as close to 0 percent as possible, of their original unsaturation content prior to hydrogenation. A titanium catalyst such as disclosed in U.S. Pat. No. 5,039,755, which is herein incorporated by reference, may also be used in the hydrogenation process.
The molecular weights of linear polymers or unassembled linear segments of polymers such as mono-, di-, triblock, etc., or the arms of star polymers before coupling are conveniently measured by Gel Permeation Chromatography (GPC), where the GPC system has been appropriately calibrated. For anionically polymerized linear polymers, the polymer is essentially monodisperse (weight average molecular weight/number average molecular weight ratio approaches unity), and it is both convenient and adequately descriptive to report the xe2x80x9cpeakxe2x80x9d molecular weight of the narrow molecular weight distribution observed. Usually, the peak value is between the number and the weight average. The peak molecular weight is the molecular weight of the main species shown on the chromatograph. For polydisperse polymers the weight average molecular weight should be calculated from the chromatograph and used. The materials used in the columns of the GPC are styrene-divinyl benzene gels or silica gels. The solvent is tetrahydrofuran and the detector is a refractive index detector.
As discussed above, the adhesive of the present invention contains from greater than 6 to less than 15, preferably 8 to 11, percent by weight of a block copolymer of styrene and butadiene and/or isoprene having a vinyl content of greater than 50% by weight, preferably from 50 to 90%wt, more preferably 70 to 80 percent by weight. The adhesive comprises more than 6 weight percent block copolymer to get the desired pressure sensitive adhesive properties and for the adhesive to be sufficiently cohesive. The maximum amount of the polymer is less than 15 percent by weight in order to keep the viscosity of the adhesive sufficiently low for the positioning adhesive application. More polymer than 15 percent can be used and good adhesion properties will be obtained but the viscosity will be unnecessarily increased.
The base block copolymer must have a sufficient molecular weight and polystyrene content to be useful for pressure sensitive adhesives. Generally, the number average molecular weight should be in the range from 65,000 to 300,000 g/mol. If the molecular weight is less than 65,000 then the polymer loses its pressure sensitive adhesive properties. If the molecular weight is more than 300,000, then the polymer is not useful for adhesive applications.
The polystyrene content preferably ranges from 10 to 40 percent by weight because this confers the right balance of cohesion and processability to the polymer.
It is known that one method to characterize tackifying resin compatibility is by determination of cloud points in suitable solvent systems. From the cloud point values obtained, the resin may be characterized as being aliphatic, aromatic, or a combination of both, polar or nonpolar, and having a high or low molecular weight. Hydrocarbon resins display wide variation in cloud point values and thus the cloud point concept is a useful method to characterize hydrocarbon resins.
MMAP cloud point is a well known measure of aromatic solubility and determines the aliphatic/aromatic character of the resin. The lower the MMAP cloud point, which is expressed in degrees centigrade, the more aromatic is the resin. A 1:2 mixture of methylcyclohexane and aniline is used as the solvent system in the MMAP cloud point determination. A standard weight of resin is dissolved in the solvent at high temperature and allowed to cool with mixing. The temperature at which the resin begins to separate out as an extra phase is determined to be the MMAP cloud point. This may be seen in the mixture as a cloudiness in the previously clear solution.
Suitable tackifiers may be selected from the group consisting of compatible C5 hydrocarbon resins, hydrogenated C5 hydrocarbon resins, styrenated C5 resins, C5/C9 resins, styrenated terpene resins, fully hydrogenated or partially hydrogenated C9 hydrocarbon resins, rosins esters, rosins derivatives and mixtures thereof. The tackifying resin must have an MMAP cloud point that is at least 45xc2x0 C. in order for the polymer/resin blend to be compatible. Commercially available hydrocarbon tackifying resins for the present invention include PICCOTAC(copyright) 95 (MMAP=95xc2x0 C.) aliphatic resin, REGALREZ(copyright) series, like REGALREZ(copyright) 1085 (85xc2x0 C.) or REGALREZ(copyright) 6108 (54xc2x0 C.) and REGALITE(copyright) series, like REGALITE(copyright) V-1100 (48xc2x0 C.) or REGALITE(copyright) S-260 (59xc2x0 C.). REGALREZ(copyright) 3102 resin (MMAP=24xc2x0 C.) does not work with this polymer because a phase stable blend cannot be achieved.
The suitable combination of resin type, block copolymer type and concentration in the formulation is required to obtain an easy, fast and homogeneous blend. For example, RP-6917, a high molecular SEBS weight polymer with 33 percent polystyrene content and a vinyl content of 70% by weight, can be easily mixed in a Z-blade mixer with PICCOTAC(copyright) 95, an aliphatic hydrocarbon resin and can quickly be homogeneously blended with REGALITE(copyright) V-1100. A hydrogenated pure aromatic resin containing a low level of aromaticity like REGALREZ(copyright) 1085 can also be used to get homogeneous blends.
Suitable plasticizers include plasticizing oils like low aromatic content (xe2x89xa630%wt, preferably xe2x89xa610%wt) hydrocarbon oils that are paraffinic or naphthenic in character. Those products are commercially available from Shell Oil Company, like SHELLFLEX(copyright), CATENEX(copyright) ONDINA(copyright) oils, KAYDOL(copyright) oil from Witco, or TUFFLO(copyright) oils from Arco. Other plasticizers include compatible liquid tackifying resins like REGALREZ(copyright) R-1018. Other ingredients might also be added, like olefin oligomers, low molecular weight polymers (xe2x89xa630,000 g/mol) like liquid polybutene or liquid polyisoprene; copolymers, like liquid styrene/isoprene copolymers or hydrogenated styrene/isoprene copolymers, and liquid alpha-olefin polymers, vegetable oils and their derivatives, paraffin and microcrystalline waxes.
It is known in the art that various other components can be added to modify e.g the odor and/or the color of the adhesives. Antioxidants and other stabilizing ingredients can also be added to protect the adhesive from degradation induced by heat, light and processing or during storage. Several types of antioxidants can be used, either primary antioxidants like hindered phenols or secondary antioxidants like phosphite derivatives or blends thereof. Examples of commercially available antioxidants are IRGANOX(copyright) 565 from Ciba-Geigy (2.4-bis-(n-octylthio)-6-(4-hydroxy-3,5-di-tertiary-butyl anilino)-1,3,5-triazine), IRGANOX(copyright) 1010 from Ciba-Geigy (tetrakis-ethylene-(3,5-di-tertiary-butyl-4-hydroxy-hydrocinnamate)methane) and POLYGUARD(copyright) HR from Uniroyal (tris-(2,4-di-tertiary-butyl-phenyl)phosphite).
The adhesive composition of the present invention typically has a viscosity of 100 to 10,000 cPs at 177xc2x0 C., preferably from 600 to 6,000 cPs at 177xc2x0 C. The adhesive typically exhibits no transfer after being peeled away from a fabric. The adhesive composition is used in articles such as disposable diapers, sanitary napkins, bed pads, incontinent pads, surgical drapes, plasters, and bandages.

Hot melt pressure sensitive positioning adhesive

Abstract: (a) from greater than 6 to less than 15 percent by weight of the total of (a), (b) and (c) of a hydrogenated styrene-(butadiene and/or isoprene)-styrene block copolymer having a vinyl content of greater than 50% by weight; and

Abstract: (b) from 50 to 80 percent by weight of the total of (a), (b) and (c) of a tackifying resin which has an aromaticity such that the MMAP cloud point is at least 45xc2x0 C.; and

Abstract: (c) from 5 to 35 percent by weight of the total of (a), (b) and (c) of a plasticizer.


The present invention relates to a multi-angle placement rack of a personal digital assistant for use in an automobile and, more particularly, to a multi-angle placement rack capable of matching a personal digital assistant with various brands and kinds of automobiles to facilitate use. The present invention comprises a placement seat, a first main body, and a second main body. The placement seat is capable of rotating and adjusting various angles of elevation. A PDA can be placed on the placement seat, which can be replaced to match different kinds of PDAs. The bottom of the placement seat joins the first main body. The first main body extends to the second main body, which can be plugged into a lighter hole of an automobile, thereby charging the PDA. The second main body is retractable to match different depths of lighter holes in various brands and kinds of automobiles.

The present invention relates to a multi-angle placement rack of a personal digital assistant (PDA) for use in an automobile and, more particularly, to a multi-angle placement rack capable of matching a PDA with various kinds of automobiles to facilitate use.
A personal digital assistant (PDA) is a new kind of portable device. Its volume is much smaller than that of a notebook computer so that it can be placed on a palm and operated. Recently, the PDAs have been much valued, and more and more people start to use them.
A PDA has many functions. For instance, it can store thousands of pieces of personal information including address lists, schedules, agenda, memos, and so on. When one needs to find out somebody""s telephone number, the PDA can quickly find out the required data for him, and it is not necessary for him to browse a notebook in a great bustle. When one needs to look up data of business cards, it is not necessary for him to search in a business card clip sweatily. All he needs to do is to click the PDA twice to exactly and quickly find out previously inputted data of business cards.
In addition to the above basic functions, most PDAs can link with a computer. For instance, electronic mails that have not been read at work can be transferred to a PDA to be read and replied on one""s commuting ways. Some PDAs can install various kinds of application programs such as spreadsheets, electronic maps, text editors, electronic books, and even games and global positioning and guiding systems.
Additionally, some PDAs have built-in wireless communication modules. In addition to being used as beepers, they can also receive real-time information such as stock market news, traffic statuses, weather predictions, real-time news, and so on. In the future, it is hopefully that PDAs can be combined with mobile phones.
FIG. 1 shows the structures of a prior art PDA 10 and its receiving seat 11. The receiving seat 11 has a receiving groove 12 thereon, which can be used to receive the PDA 10. The receiving seat 11 has a press button 13 near the front edge thereof. The press button 13 is pressed so that the PDA 10 can be conveniently taken out for use.
However, the above PDA 10 uses batteries of limited electricity. Because existent PDAs cannot be combined with an automobile, they cannot use electricity from the automobile. Therefore, a driver cannot use a lot of functions of the PDA 10 when driving an automobile.
Accordingly, the above prior art PDA has inconvenience and drawbacks in practical use. The present invention aims to resolve the above problems in the prior art.
The primary object of the present invention is to provide a multi-angle placement rack of a PDA for use in an automobile. The placement rack can effectively provide stable electricity for a PDA so that a driver can use spreadsheets, electronic maps, text editors, electronic books, and even games and global positioning and guiding systems of the PDA. Moreover, when a wireless communication module is built in the PDA, in addition to being used as a beeper, the PDA can also receive real-time information such as stock market news, traffic statuses, weather predictions, real-time news, and so on, hence facilitating use of the driver.
To achieve the above object, the present invention provides a multi-angle placement rack of a PDA for use in an automobile. The placement rack comprises a placement seat, a first main body, and a second main body. The placement seat is capable of rotating and adjusting various angles of elevation. A PDA can be placed on the placement seat, which can be replaced to match different kinds of PDAs. The bottom of the placement seat joins the first main body. The first main body extends to the second main body, which can be plugged into a lighter hole of an automobile, thereby charging the PDA. The second main body is retractable to match different depths of lighter holes of various brands and kinds of automobiles.
The various objects and advantages of the present invention will be more readily understood from the following detailed description when read in conjunction with the appended drawing, in which:

Multi-angle placement rack of personal digital assistant for use in an automobile


A composition that includes a fluoropolymer comprising interpolymerized units derived from a cure site monomer comprising a nitrile group; and (b) a catalyst composition comprising a compound having the formula R1C(OR2)xe2x95x90NH, and salts thereof, where R1 and R2, independently, are a substituted or unsubstituted alkyl, aryl, aralkyl, or alkenyl group, as well as a method for curing this composition and cured articles prepared from this composition.

This invention relates to fluoropolymer compositions having nitrile group-containing cure-site components.
Fluorine-containing polymers (also known as xe2x80x9cfluoropolymersxe2x80x9d) are a commercially useful class of materials. Fluoropolymers include, for example, crosslinked fluoroelastomers, and semi-crystalline or amorphous fluoroplastics. Fluoroplastics are generally of high thermal stability and are particularly useful at high temperatures. They may also exhibit extreme toughness and flexibility at very low temperatures. Some have very low dielectric loss and high dielectric strength, and may have unique low friction properties.
Fluoroelastomers exhibit significant tolerance to high temperatures and harsh chemical environments. Consequently, they are particularly useful as seals, gaskets, and other molded parts in systems that are exposed to elevated temperatures and/or corrosive chemicals. Such parts are widely used in the chemical processing, semiconductor, aerospace, and petroleum industries, among others.
Fluoroelastomers often include a cure-site component to facilitate cure in the presence of a catalyst. One class of useful cure-site components includes nitrile group-containing monomers. Organotin catalysts are typically used as cure catalysts. Such catalysts, however, are toxic and can leave undesirable extractable metal residues in the cured product.
In one aspect, the invention relates to a composition that includes (a) a fluoropolymer having interpolymerized units derived from a cure site monomer comprising a nitrile group; and (b) a catalyst composition that includes a compound having the formula R1C(OR2)xe2x95x90NH, and salts thereof, where R1 and R2, independently, are a substituted or unsubstituted alkyl, aryl, aralkyl, or alkenyl group. xe2x80x9cSubstitutedxe2x80x9d means substituted by substituents that do not interfere with the desired product. Examples of suitable substituents include halogen (e.g., chlorine, fluorine, bromine, iodine), cyano, alkoxy, and carboxy groups. In addition, one or more of the carbon atoms may be substituted by a heteroatom such as oxygen or nitrogen. Specific examples of useful groups for R1 include fluoroalkyl, perfluoroalkyl, and perfluoro (poly)ether groups (e.g., as described in U.S. Pat. No. 5,266,650). Specific examples of useful groups for R2 include fluoroalkyl and perfluoroalkyl groups. In yet another aspect, the invention provides a method for curing this composition, as well as the cured compositions.
The compositions retain the advantages of the use of nitrile group-containing cure site monomers such as the high temperature performance properties and chemical resistance typically achieved when organotin compounds are used as the catalyst system with such cure site monomers. At the same time, the compositions exhibit markedly improved compression set values and eliminate the presence of extractable metal residues resulting from the use of organometal catalysts. In addition, the cured compositions, in some cases, may be optically clear in the absence of carbon black or other colorants. xe2x80x9cOptically clearxe2x80x9d means that the composition is substantially transparent and does not show severe discoloration.
Because the compositions are free of extractable organometal compounds, they may be characterized as being xe2x80x9cclean.xe2x80x9d This result is achieved without the need to employ any additional processing steps to eliminate the organometal compounds. The compositions are useful in applications where polymer stability (e.g., thermal stability), chemical resistance, and/or optical clarity are important. They are also useful in silicon wafer fabrication.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and from the claims.
Suitable fluoropolymers include interpolymerized units derived from a nitrile group-containing monomer and, preferably, at least two principal monomers. Examples of suitable candidates for the principal monomer include perfluoroolefins (e.g., tetrafluoroethylene and hexafluoropropene), perfluorovinyl ethers (e.g., perfluoroalkyl vinyl ethers and perfluoroalkoxy vinyl ethers), and hydrogen-containing monomers such as olefins (e.g., ethylene, propylene, and the like) and partially-fluorinated olefins such as vinylidene fluoride.
Suitable perfluorinated vinyl ethers include those of the formula:
xe2x80x83CF2xe2x95x90CFO(Rxe2x80x2fO)a(Rxe2x80x3fO)bRfxe2x80x83xe2x80x83(1)
where Rxe2x80x2f and Rxe2x80x3f are the same or are different linear or branched perfluoroalkylene groups of 1-6 carbon atoms; a and b are, independently, 0 or an integer from 1 to 10; and Rf is a perfluoroalkyl group of 1-6 carbon atoms.
A preferred class of perfluoroalkyl vinyl ethers includes compositions of the formula:
CF2xe2x95x90(CFO(CF2CFXO)nRfxe2x80x83xe2x80x83(2)
wherein X is F or CF3; n is 0-5, and Rf is a perfluoroalkyl group of 1-6 carbon atoms.
Most preferred perfluoroalkyl vinyl ethers are those where, in reference to either Formula 1 or 2 above, n is 0 or 1 and Rf contains 1-3 carbon atoms. Examples of such perfluorinated ethers include perfluoromethyl vinyl ether, perfluoroethyl vinyl ether, and perfluoropropyl vinyl ether.
Other useful perfluorinated monomers include those compounds of the formula:
CF2xe2x95x90(CFO[(CF2)m(CFZ)uO]nRfxe2x80x83xe2x80x83(3)
where Rf is a perfluoroalkyl group having 1-6 carbon atoms, m is 0-2, u is 0 or 1, n is 0-5, provided that both m and n are not zero, and Z is F or CF3. Preferred members of this class are those in which Rf is CF3 or C3F7, m is 0, and n is 1.
Additional perfluoroalkyl vinyl ether monomers useful in the invention include those of the formula:
CF2xe2x95x90CFO[(CF2CF(CF3)O)g(CF2)k(OCF2)p]CxF2x+1xe2x80x83xe2x80x83(4)
where g is 0 or an integer from 1-5, k is 0 or an integer from 1-6, p is 0-3, and x is 1-5, provided that when k is 0, p is also 0. Preferred members of this class include compounds where g is 0 or 1, k is 0 or 1, p is 0 or 1, and x is 1.
Perfluoroalkoxy vinyl ethers useful in the invention include those of the formula:
CF2xe2x95x90CFO(CF2)t(CFZ)uO(CF2O)wCxF2x+1xe2x80x83xe2x80x83(5)
wherein Z is F or CF3, t is 1-3, u is 0-1, w is 0-3, and x is 1-5, preferably 1. specific, representative, examples of useful perfluoroalkoxy vinyl ethers include CF2xe2x95x90CFOCF2OCF2CF2CF3, CF2xe2x95x90CFOCF2)OCF3, CF2xe2x95x90CFO(CF2)3OCF3, and CF2xe2x95x90CFOCF2CF2OCF3.
Mixtures of perfluoroalkyl vinyl ethers and perfluoroalkoxy vinyl ethers may also be employed.
Perfluoroolefins useful in the invention include those of the formula:
CF2xe2x95x90CFxe2x80x94R5f,xe2x80x83xe2x80x83(6)
where R5f is fluorine or a perfluoroalkyl of 1 to 8, preferably 1 to 3, carbon atoms.
In addition, partially-fluorinated monomers or hydrogen-containing monomers such as olefins (e.g., ethylene, propylene, and the like), and vinylidene fluoride can be used in the fluoropolymer of the invention.
One example of a useful fluoropolymer is composed of tetrafluoroethylene and at least one perfluoroalkyl vinyl ether as principal monomer units. In such copolymers, the copolymerized perfluorinated ether units constitute from about 15 to about 50 mole percent (mol %) (more preferably 15 to 35 mol %) of total monomer units present in the polymer.
One or more other fluoropolymers may be incorporated into the fluoropolymer having interpolymerized units derived from a cure site monomer comprising a nitrile group. In addition, one or more other fluoropolymers (which may include one or more copolymers) may be blended with the fluoropolymer (which may comprise a copolymer) having interpolymerized units derived from a cure site monomer comprising a nitrile group. Such other fluoropolymers useful in a blend and/or copolymer include the entire array described above. The other fluoropolymer(s) may lack interpolymerized units derived from a cure site monomer comprising a nitrile group and/or may include reactive sites adapted to a selected curative system. For example, two different fluoropolymers, each having interpolymerized units derived from a cure site monomer comprising a nitrile group may be blended to provide the fluoropolymer for the present invention.
Another fluoropolymer may be included along with another curative, such as described below, to provide particular properties. For example, a fluoropolymer suitable for peroxide curing and a peroxide curative may be included to improve chemical stability. Such a blend balances the thermal stability and the chemical stability of the resultant blend, and also may provide economic benefits. These other curatives also may be used to cure a blend of nitrile-containing fluoropolymers without the need to include a fluoropolymer lacking nitrile groups.
The fluoropolymers may be prepared by methods known in the art. For example, the polymerization process can be carried out by any free-radical polymerization of the monomers, e.g., in solutions, emulsions, or suspensions in an organic solvent or water. Polymerization in an aqueous emulsion or suspension often is preferred because of the rapid and nearly complete conversion of monomers, easy removal of the heat of polymerization, and ready isolation of the polymer. Emulsion polymerization typically involves polymerizing monomers in an aqueous medium in the presence of a free-radical initiator system, e.g., a persulfate such as ammonium persulfate, potassium permanganate, or organic peroxides, often in the presence of reducing agents and a non-telogenic fluorinated surfactant, such as APFO (ammonium perfluorooctanoate).
Aqueous emulsion polymerization can be carried out continuously under steady-state conditions in which, for example, monomers, water, surfactants, buffers, and catalysts are fed continuously to a stirred reactor under optimum pressure and temperature conditions while the resulting emulsion is removed continuously. An alternative technique is batch or semibatch polymerization by feeding the ingredients into a stirred reactor and allowing them to react at a set temperature for a specified length of time or by charging ingredients into the reactor and feeding the monomer into the reactor to maintain a constant pressure until a desired amount of polymer is formed.
The free-radical polymerization process can also be carried out in the presence of a perfluorosulfinate and an oxidizing agent to improve the processability of the resulting fluoropolymer composition. Such oxidizing agents are capable of converting the sulfinate to a sulfonyl moiety. The produced sulfonyl radical is believed to eliminate SO2 and form a fluorinated radical that initiates the polymerization of the ethylenically unsaturated monomers. A number of useful oxidizing agents are known as taught in U.S. Pat. No. 5,285,002 and U.S. Pat. No. 5,639,837. Representative examples of such useful oxidizing agents are sodium, potassium, and ammonium persulfates, perphosphates, perborates, percarbonates, bromates, chlorates, and hypochlorites. Other useful oxidizing agents include cerium IV compounds such as (NH4)2Ce(NO3)6. The amount of oxidizing agent used can vary depending on the particular oxidizing agent and sulfinate employed. Typically an equimolar amount or less (based on the amount of sulfinate) is used.
Perfluorosulfinates useful for this purpose include those described in U.S. Pat. No. 5,285,002 and represented by the general formula:
R3fSO2M1/xxe2x80x83xe2x80x83(7)
or
R2f[SO2M1/x]jxe2x80x83xe2x80x83(8)
where R3f represents a monovalent fluoroaliphatic radical having, for example, from 1 to 20 carbon atoms, preferably 4 to 10 carbon atoms; R2f represents a polyvalent, preferably divalent, fluoroaliphatic radical having, for example, from 1 to 20 carbon atoms, preferably from 2 to 10 carbon atoms; M represents a hydrogen atom or cation with valence x, which is 1 or 2; and j is 1 to 4, preferably 1 or 2.
In addition to the sulfinate, other reducing agents can be present, such as sodium, potassium or ammonium sulfites, bisulfite, metabisulfite, hyposulfite, thiosulfite, phosphite, sodium or potassium formaldehyde sulfoxylate or hypophosphite. Activators such as ferrous, cuprous, and silver salts, may also be present.
The amount of fluoroaliphatic sulfinate employed in the polymerization process can vary, depending, for example, on the molecular weight of polymer desired. Preferably the amount of fluoroaliphatic sulfinate is from 0.001 to 50 mole percent, and most preferably from 0.01 to 10 mole percent, of sulfinate compound based on total quantity of monomers.
The nature and the amount of end groups are not critical to the success in curing the fluoroelastomer. For example, the polymer can contain SO3(xe2x88x92) end groups generated by an APS/sulfite system, or the polymer may contain COO(xe2x88x92) end groups generated by an APS initiator system or the fluoroelastomer can have xe2x80x9cneutralxe2x80x9d end groups, e.g., those generated by the use of fluorosulfinate initiator systems or organic peroxides. The number of end groups can be significantly reduced by chain transfer agents of any kind. If desired, such as for improved processing, the presence of strong polar end groups such as SO3(xe2x88x92) can be minimized and in the case of COO(xe2x88x92) end groups, the amount can be reduced through post treatments (decarboxylation).
The cure site component is capable of curing the fluoropolymer. The cure site component generally will comprise at least one nitrile group-containing cure site monomer. The cure site component can be partially or fully fluorinated. Useful nitrile group-containing cure site monomers include nitrile-containing fluorinated olefins and nitrile-containing fluorinated vinyl ethers, such as depicted below:
CF2xe2x95x90CFO(CF2)LCNxe2x80x83xe2x80x83(9)
CF2xe2x95x90CFO[CF2CF(CF3)O]q(CF2)yOCF(CF3)CNxe2x80x83xe2x80x83(10)
CF2xe2x95x90CF[OCF2CF(CF3)]rO(CF2)tCNxe2x80x83xe2x80x83(11)
where, in reference to the above formulas: L=2-12; q=0-4; r=1-2; y=1-6; and t=1-10. Representative examples of such a monomer include perfluoro(8-cyano-5-methyl-3,6-dioxa-1-octene), CF2xe2x95x90CFO(CF2)5CN, and CF2xe2x95x90CFO(CF2)3OCF(CF3)CN.
The fluoropolymer compositions are cured using an imidate catalyst having the formula R1C(OR2)xe2x95x90NH, and salts thereof, where R1 and R2, independently, are a substituted or unsubstituted alkyl group (e.g., a C1 to C20 alkyl group), aryl group (e.g., a phenyl or naphthyl group), aralkyl group (e.g., a tolyl group), or alkenyl group (e.g., a C1 to C20 alkenyl group). Examples of suitable substituents include halogen (e.g., chlorine, fluorine, bromine, iodine), cyano, alkoxy, and carboxy groups. In addition, one or more of the carbon atoms may be substituted by a heteroatom such as oxygen or nitrogen. Specific examples of useful groups include fluoroalkyl (e.g., a C1 to C20 fluoroalkyl group), perfluoroalkyl (e.g., a C1 to C20 perfluoroalkyl group), and perfluoro polyether groups (e.g., as described in U.S. Pat. No. 5,266,650). Preferably, R1 is a perfluoroalkyl group and R2 is a C1 to C10 alkyl group.
An example of a useful imidate catalyst is C7F15C(OCH3)xe2x95x90NH. These imidates may be prepared, for example, by reacting a perfluoroalkylnitrile or perfluroalkyldinitrile with an alcohol, as described in U.S. Pat. No.3,523,132; ZH. OBS. KHIMI, Vol. 36(5), pages 862-871 (1966); and J. ORG. CHEM., Vol. 30, page 3724 (1965); which are herein incorporated by reference. Examples of commercially available imidates include (a) CH3Oxe2x80x94Cxe2x95x90NHxe2x80x94C4H8xe2x80x94C(OCH3)xe2x95x90NH (2HCL)(Aldrich Chemical Co.); (b) nxe2x80x94C11H23xe2x80x94C(OCH3)xe2x95x90NH (HCl) (Maybridge); and (c) CH3Oxe2x80x94Cxe2x95x90NHxe2x80x94C2H4xe2x80x94Sxe2x80x94Sxe2x80x94C2H4C(OCH3)xe2x95x90NH (2HCl) (Fluka/ICN/Sigma).
Within the general imidate formula, R1C(OR2)xe2x95x90NH, preferred R2 groups include C1-C10 alkyls, which may be branched, xe2x80x94CH2xe2x80x94Rf, xe2x80x94CH2CH2Rf, wherein Rf is a perfluoro or partially-fluorinated C1-C10 group. Preferred R1 groups include C4-C10 alkyls. Especially preferred R1 groups include C8 alkyls, CF3xe2x80x94Oxe2x80x94(CF2)mxe2x80x94Oxe2x80x94CF(CF3)xe2x80x94, wherein m is 1-4, and C3F7xe2x80x94(xe2x80x94Oxe2x80x94CF(CF3)xe2x80x94CF2)nxe2x80x94Oxe2x80x94CF(CF3)xe2x80x94, wherein n is 0-3.
Compounds having more than one imidate group are also useful, e.g., HNxe2x95x90C(OR2)xe2x80x94(CF2)mxe2x80x94R1C(OR2)xe2x95x90NH, wherein m is 0-20, preferably 1-9, more preferably 1-5.
The imidates can be used in their salt form, for example, HCl-salt, or a salt of another inorganic acid, or the salt of an organic acid such as carboxylic or sulfonic acid. One specific example of such a salt includes the anion C7F15COO(xe2x88x92).
In addition, alcohols can be used with the imidate catalysts of the invention. Such alcohols preferably have boiling points of at least 70xc2x0 C., as do the imidates. Alcohols from ethanol through octanol are preferred. The amount of alcohol used ranges from about 0 to 100 weight percent, relative to the amount of imidate. That is, at 100 weight percent, the weight of alcohol and imidate are equivalent.
The level of imidate units in the overall fluoropolymer composition is that amount sufficient to provide the desired physical properties in a selected material after curing. This level can vary from about 0.05 to 10 parts imidate per 100 parts fluoropolymer (by weight) (phr), more preferably from 0.1 to 5 phr.
The fluoropolymer compositions can be cured using one or more peroxide curatives along with the imidate catalysts. Suitable peroxide curatives generally are those that generate free radicals at curing temperatures. Dialkyl peroxide and bis(dialkyl peroxide), each of which decomposes at a temperature above 50xc2x0 C., are especially preferred. In many cases it is preferred to use a di-tertiarybutyl peroxide having a tertiary carbon atom attached to peroxy oxygen atom. Among the most useful peroxides of this type are 2,5-dimethyl-2,5-di(tertiarybutylperoxy)hexyne-3 and 2,5-dimethyl-2,5-di(tertiarybutylperoxy)hexane. Other peroxides can be selected from such compounds as dicumyl peroxide, dibenzoyl peroxide, tertiarybutyl perbenzoate, a,axe2x80x2-bis(t-butylperoxy-diisopropylbenzene), and di[1,3-dimethyl-3-(t-butylperoxy)-butyl]carbonate. Generally, about 1 to 3 parts of peroxide per 100 parts of fluoropolymer is used.
The fluoropolymer compositions can include any of the adjuvants commonly employed in curable fluoropolymer formulations. For example, one material often blended with a fluoropolymer composition as a part of the peroxide curative system is a coagent (sometimes also referred to as a co-curative) composed of a polyunsaturated compound that is capable of cooperating with the curative to provide a useful cure. These coagents can generally be added in an amount equal to between 0.1 and 10 parts per hundred parts fluoropolymer, preferably between 1 and 5 parts per hundred parts fluoropolymer. Examples of useful coagents include triallyl cyanurate; triallyl isocyanurate; tri(methylallyl isocyanurate; tris(diallylamine)-s-triazine; triallyl phosphite; N,N-diallyl acrylamide; hexaallyl phosphoramide; N,N,Nxe2x80x2,Nxe2x80x2-tetraalkyl tetraphthalamide; N,N,Nxe2x80x2,Nxe2x80x2-tetraallyl malonamide; trivinyl isocyanurate; 2,4,6-trivinyl methyltrisiloxane; and tri(5-norbornene-2-methylene)cyanurate. Particularly useful is triallyl isocyanurate.
Other coagents that can be used with the peroxide curative include the bis-olefins disclosed in EPA 0 661 304A1, EPA 0 784 064 A1 and EPA 0 769 521 A1.
The fluoropolymer compositions can also be cured by combining other types of curatives known to be useful in curing nitrile-containing fluoropolymers along with the integral imidate, if any undesirable features of the known curing system is tolerable. Examples of such curatives include peroxides, aromatic amino compounds including aromatic amino phenols, bis-aminophenols (e.g., as described in U.S. Pat. No. 5,767,204 and U.S. Pat. No. 5,700,879), bis-amidrazones, bis-amidooximes (e.g., as described in U.S. Pat. No. 5,621,145), and ammonium salts (e.g., as described in U.S. Pat. No. 5,565,512). Organometallic compounds of arsenic, antimony and tin also can be used, for example as described in U.S. Pat. Nos. 4,281,092; and 5,554,680. Particular examples include allyl-, propargyl-, triphenyl- allenyl-, and tetraphenyltin and triphenyltin hydroxide. These additional curatives are preferably added to reach total curative amounts (imidate catalyst plus other curative(s)) from about 0.05 to 10 phr, more preferably 0.1 to 5 phr.
It may be advantageous to add one or more onium salts to the fluoropolymer compositions to obtain improved polymer properties. Examples of suitable onium salts are described in U.S. Pat. No. 4,882,390. Specific examples include triphenylbenzyl phosphonium chloride, tributyl alkyl phosphonium chloride, tributyl benzyl ammonium chloride, tetrabutyl ammonium bromide, and triarylsulfonium chloride. The phosphonium compounds are preferred.
The combination of catalyst, optional imidate(s), and optional curative(s) is generally from about 0.01 to about 10 mol % (more preferably from about 0.1 to about 5 mol %) of the total fluoropolymer amount.
Additives such as carbon black, stabilizers, plasticizers, lubricants, fillers, and processing aids typically utilized in fluoropolymer compounding can be incorporated into the compositions, provided they have adequate stability for the intended service conditions. In particular, low temperature performance can be enhanced by incorporation of perfluoropolyethers. See, for example, U.S. Pat No. 5,268,405.
Carbon black fillers are typically also employed in fluoropolymers as a means to balance modulus, tensile strength, elongation, hardness, abrasion resistance, conductivity, and processability of the compositions. Suitable examples include MT blacks (medium thermal black) designated N-991, N-990, N-908, and N-907; FEF N-550; and large particle size furnace blacks. When used, 1-70 phr of large size particle black is generally sufficient.
Fluoropolymer fillers may also be present in the compositions. Generally, from 1 to 50 parts filler per hundred parts base fluoropolymer resin of one or more fluoropolymer fillers is used. The fluoropolymer filler can be finely divided and easily dispersed as a solid at the highest temperature utilized in fabrication and curing of the fluoroelastomer composition. By solid, it is meant that the filler material, if partially crystalline, will have a crystalline melting temperature above the processing temperature(s) of the fluoroelastomer(s). The preferred way to incorporate fluoropolymer filler is by blending latices; this procedure and various kinds of fluoropolymer fillers are described in U.S. Ser. No. 09/495,600, filed Feb. 1, 2000.
Such fillers typically have melting points ranging from 100 to 300xc2x0 C. Examples of useful fillers include low molecular weight polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoropropyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropene copolymer (FEP).
One or more acid acceptors can also be added to the formulations, though, where the presence of extractable metallic compounds is undesirable (such as for semiconductor applications) the use of inorganic acid acceptors should be minimized, and preferably avoided altogether. Commonly used acid acceptors include, for example, zinc oxide, calcium hydroxide, calcium carbonate, magnesium oxide, etc. These compounds generally are used in the fluoropolymer formulation to bind any HF or other acids that might be generated at the high temperatures where fluoropolymers must function.
The curable fluoropolymer compositions of the invention may also be combined with other curable fluoropolymer compositions such as peroxide-curable fluoropolymer compositions. These additional curable fluoropolymer compositions typically employ small amounts of cure site monomers as a comonomer. Suitable cure site monomers are those which, when combined with a curative (e.g., a peroxide) and, preferably, a coagent, will provide a cured composition. Preferably these cure site monomers include at least one halo group (e.g., a bromo or an iodo group).
The curable fluoropolymer compositions can be prepared by mixing the fluoropolymer, the imidate catalyst, the selected additive or additives, additional curatives (if any), onium salts (if any), and other adjuvants (if any), in conventional rubber processing equipment. The desired amounts of compounding ingredients and other conventional adjuvants or ingredients can be added to the unvulcanized fluorocarbon gum stock and intimately admixed or compounded therewith by employing any of the usual rubber mixing devices such as internal mixers, (e.g., Banbury mixers), roll mills, or any other convenient mixing device. The temperature of the mixture during the mixing process typically should not rise above about 120xc2x0 C. During mixing, it is preferable to distribute the components and adjuvants uniformly throughout the gum for effective cure.
The mixture is then processed and shaped, for example, by extrusion (for example, in the shape of a hose or hose lining) or molding (for example, in the form of an O-ring seal). The shaped article can then be heated to cure the gum composition and form a cured article.
Pressing of the compounded mixture (i.e., press cure) usually is conducted at a temperature between about 95xc2x0 C. and about 230xc2x0 C., preferably between about 150xc2x0 C. and about 205xc2x0 C., for a period of from 1 minute to 15 hours, typically from 5 minutes to 30 minutes. A pressure of between about 700 kPa and about 20,600 kPa is usually imposed on the compounded mixture in the mold. The molds first may be coated with a release agent and prebaked. The molded vulcanizate is then usually post-cured (e.g., oven-cured) at a temperature usually between about 150xc2x0 C. and about 300xc2x0 C., typically at about 230xc2x0 C., for a period of from about 2 hours to 50 hours or more, generally increasing with the cross-sectional thickness of the article. For thick sections, the temperature during the post cure is usually raised gradually from the lower limit of the range to the desired maximum temperature. The maximum temperature used is preferably about 300xc2x0 C., and is held at this value for about 4 hours or more.
The fluoropolymer compositions are useful in production of articles such as O-rings, gaskets, tubing, and seals. Such articles are produced by molding a compounded formulation of the fluoropolymer composition with various additives under pressure, curing the part, and then subjecting it to a post-cure cycle. The curable compositions formulated without inorganic acid acceptors are particularly useful for applications such as seals and gaskets for manufacturing semiconductor devices, and in seals for high temperature automotive uses.
The invention will now be described further by way of the following examples.