JPS6348884B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to curable polymer latexes, and more particularly to self-curing polymer latexes. Various self-curing latexes are well known in the art. For example, acrylic acid/styrene/
It is known in the art that blends of carboxylated latexes such as butadiene terpolymers with melamine-formaldehyde resins or urea-formaldehyde resins are self-curing, that is, they form curable compositions that cure at elevated temperatures. ing. Other self-curing latex systems use carboxylated latexes that are crosslinked with polyvalent cations or cationic polymers. Such latexes have the disadvantage of being PH-dependent and very sensitive to water, solvents and other chemicals. Therefore, it is highly desirable to provide a polymer latex that is self-curing without the formation of by-products and that upon curing forms a film or adhesive with excellent physical properties and improved resistance to water and organic solvents. desirable. It would also be desirable to provide a method for making polymers containing both pendant acid groups and pendant oxazoline groups. The present invention provides such polymers and methods. In one aspect, the present invention provides a curable latex composition comprising a discrete population of polymer particles, the polymer portion of which contains (a) a co-reactive monomer containing a pendant group capable of reacting with an oxazoline group to form a covalent bond; , (b) General formula [wherein R ¹ is an acyclic organic group having addition polymerizable unsaturation; each R ² is independently hydrogen, halogen, or an inert substituted organic group; n is 1 or 2]; and (c) at least one other addition-polymerizable monomer that does not contain a co-reactive group or an oxazoline group (provided that the oxazoline group and the co-reactive group are suspended). A curable latex composition is provided. In one aspect, both (a) the pendant co-reactive group and (b) the pendant oxazoline group are present in the same latex particle in at least a portion of the latex particles. In a slightly different embodiment, (a) the pendant reactive groups are present on one portion of the latex particles, and (b) the pendant oxazoline groups are present on a second, separate portion of the latex particles. In another aspect, the invention provides a method for making a latex comprising a discrete population of particles containing both pendant co-reactive weak acid groups and pendant oxazoline groups, comprising the steps of: (a) pendant weak acid groups; and at least one addition-polymerizable monomer copolymerizable with the weak acid monomer at a pH in the range of 1 to 6. producing a latex containing particles of a polymer, and then (b) determining the pH of the produced latex;
is adjusted to a value at which the addition-polymerizable oxazoline does not substantially react or hydrolyze under conditions suitable for its polymerization, and (c) this latex has (1) the general formula [wherein R ¹ is an acyclic organic group having addition polymerizable unsaturation; each R ² is independently hydrogen, halogen, or an inert substituted organic group; n is 1 or 2]; (2) at least one other monomer that does not contain pendant co-reactive weak acid groups or pendant oxazoline groups; and (d) a mixture of these monomers. The second monomer mixture is polymerized in or around the pendant co-reactive weak acid group-containing polymer particles. Surprisingly, the latex of the present invention exhibits excellent tensile strength and elongation upon drying and curing, as well as excellent water and solvent resistance. Such latexes are therefore useful in a variety of applications including films, coatings, adhesives, binders for nonwovens, and the like. The latex compositions of the present invention include (a) discrete groups of polymer particles containing both pendant oxazoline groups and pendant co-reactive weak acid groups; and/or (b) at least a portion of the particles containing pendant oxazoline groups. A second separate portion of the particles then comprises a separate group of polymer particles containing pendant co-reactive groups. The oxazoline used herein is represented by the following general formula. where R ¹ is an acyclic organic group with addition polymerizable unsaturation; each R ² is independently hydrogen, halogen, or an inert substituted organic group, and n
is 1 or 2. Preferably, R ¹ is

[Formula] (R ³ is hydrogen or an alkyl group). Most preferably R ¹ is an isopropenyl group. Each R ² is preferably hydrogen or an alkyl group, with hydrogen being most preferred. n is preferably 1. Most preferably the oxazoline is 2
-isopropenyl-2-oxazoline. The oxazoline-modified polymer also includes repeating units derived from at least one monomer that is not an oxazoline and is copolymerizable with the oxazoline. A wide variety of addition polymerizable polymers are copolymerizable with the oxazoline and are suitable herein. Suitable monomers include, for example, monovinyl aromatics, alkenes, esters of α,β-unsaturated carboxylic acids, carboxylic acid esters containing addition polymerizable unsaturation in the ester group, halogenated alkenes, and acyclic conjugated dienes. . Small amounts of cross-linking monomers such as divinylbenzene can also be used. “Monovinyl aromatic” as used herein is the formula

[Formula] (R is hydrogen or lower alkyl, e.g. alkyl having 1 to 4 carbon atoms) has an aromatic nucleus containing 6 to 10 carbon atoms (the aromatic nucleus is substituted with alkyl or halogen) (including monomers). Typical of these monomers are styrene; α-methylstyrene; ortho-,
meta- and para-methylstyrene; ortho;
meta- and para-ethylstyrene; o,p-dimethylstyrene; o,p-diethylstyrene; t
-butylstyrene; p-chlorostyrene; p-bromostyrene; o, p-dichlorostyrene; o,
p-dibromostyrene; vinylnaphthalene; various vinyl (alkylnaphthalenes) and vinyl (halonaphthalenes) and copolymerizable mixtures thereof. Styrene and vinyltoluene are preferred in consideration of price, availability, ease of use, etc.
Styrene is particularly preferred as monovinyl aromatic monomer. Alkenes suitable for use in the present invention include:
Monounsaturated aliphatic organic compounds such as ethylene,
n- and iso-propylene, various butenes,
Mention may be made of pentenes and hexenes as well as alkenes containing various substituents inert to polymerization. Unsubstituted _C2 - _C8 alkenes are preferred, unsubstituted
Most preferred are _C2 - _C4 alkenes. Esters of α,β-ethylenically unsaturated carboxylic acids useful in this invention include soft acrylates whose homopolymers have a glass transition temperature (Tg) of less than about 25°C, such as benzyl acrylate, butyl acrylate, Examples include butyl acrylate, cyclohexyl acrylate, dodecyl acrylate, ethyl acrylate, 2-ethylbutyl acrylate, 2-ethylhexyl acrylate, heptyl acrylate, hexyl acrylate, isobutyl acrylate, isopropyl acrylate, methyl acrylate, and propyl acrylate. Hard acrylates whose homopolymers have a Tg of about 25°C or higher, such as 4-biphenyl acrylate and t
It is also suitable to use -butyl acrylate; and soft methacrylates such as secondary butyl methacrylate, ethyl methacrylate, isobutyl methacrylate, isobutyl methacrylate, isopropyl methacrylate, methyl methacrylate and propyl methacrylate. Butyl acrylate and ethyl acrylate are particularly preferred among the acrylates because of their price, availability, and well-known properties. Methyl methacrylate is particularly preferred among the methacrylates because of its price, availability, and well-known properties. Halogenated alkenes useful in the present invention include:
Examples include vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride, and various polychloro-, polyfluoro-, and polybromoalkenes. Acyclic aliphatic conjugated dienes usefully used in the present invention typically include these compounds having 4 to 9 carbon atoms, such as 1,3-butadiene;
-methyl-1,3-butadiene; 2,3-dimethyl-1,3-butadiene; pentadiene; and 2-neopentyl-1,3-butadiene. Other hydrocarbon congeners of 1,3-butadiene such as 2-chloro-1,3-butadiene and 2-cyano-1,3-butadiene; substituted linear conjugated pentadiene; linear and side-chain conjugated hexadiene; 4-9 Other straight-chain and side-chain conjugated dienes having 5 carbon atoms; and comonomer mixtures thereof are also suitable. 1,3-butadiene hydrocarbon monomers, such as those described above, are preferred because they provide interpolymers with particularly desirable properties. 1,3-
Butadiene is the most preferred acyclic aliphatic conjugated diene because of its price, availability, and excellent properties of the interpolymers made therefrom. It is of course possible, if desired, to use mixtures of two or more of the abovementioned monomers. Most preferred among the above monomers are styrene, mixtures of styrene and butadiene, butyl acrylate, methyl methacrylate, and vinyl acetate. The proportions of monomers used in the oxazoline modified latex can vary considerably depending on the particular end use of the composition. Typically, however, oxazolines are used in relatively small amounts, such as from 0.1 to 20%, preferably from 1 to 10%, by weight of the monomers. Generally, the oxazoline is used primarily to impart the desired self-curing properties to the latex composition, while other monomers are used to impart other properties to the composition. For example, in the preferred oxazoline-modified styrene/butadiene latex, the oxazoline-modified polymer advantageously exhibits similar physical properties (eg, glass transition temperature and hardness) normally associated with styrene/butadiene polymers. However, certain properties of the polymer, particularly adhesion and cross-linking, are generally increased by the inclusion of oxazoline monomers. The latexes of the present invention further include pendant co-reactive groups. These groups can react with oxazolines to form covalent bonds (hereinafter referred to as "co-reactive"). Co-reactive monomers (ie, monomers containing pendant co-reactive groups) for use in the present invention are those containing pendant co-reactive groups that can react with oxazoline groups to form covalent bonds. It is understood that the reaction of such co-reactive groups with the oxazoline group typically, although not necessarily, opens the oxazoline ring. Typically, the pendant group of the co-reactive monomer contains a reactive hydrogen atom. Examples of co-reactive groups containing active hydrogen atoms include strong acid groups, weak acid groups, aliphatic alcohol groups, aromatic alcohol groups (i.e. phenolic groups), amine groups, and amide groups (i.e. -
CONH ₂ and -CONH- group). Generally, among these groups, those with high reactivity,
That is, highly unstable substances such as acids and aromatic alcohols are preferred here. Such highly reactive groups generally react more rapidly with the oxazoline ring under milder conditions than less reactive groups such as amines and aliphatic alcohols. Amide groups generally exhibit intermediate reactivity. Particularly preferred are monomers containing pendant strong or weak acid groups that include acid anhydride groups. Such monomers include ethylenic monomers containing acid groups or acid anhydride groups such as carboxylic acid groups and sulfonic acid groups. Sulfoethyl acrylate is an example of a suitable sulfonic acid-containing monomer. Examples of suitable monomers containing carboxylic acid groups include itaconic acid, acrylic acid, methacrylic acid,
Mention may be made of fumaric acid, maleic acid, vinylbenzoic acid, and isopropenylbenzoic acid. More preferred are acrylic acid, methacrylic acid,
Mention may be made of fumaric acid, itaconic acid, and maleic acid. Maleic anhydride is an example of a suitable monomer containing an acid anhydride group. Suitable co-reactive monomers containing phenolic groups include ortho- and meta-vinylphenols. Suitable co-reactive monomers containing aliphatic hydroxy groups include, for example, hydroxyethyl acrylate, hydroxypropyl methacrylate and N-hydroxymethyl-N-methylacrylamide. Styrene derivatives with aliphatic hydroxy groups are also useful. Suitable monomers containing amide groups include acrylamide, methacrylamide, vinylacetamide and alpha-chloroacrylamide. N-methylacrylamide and N-methylmethacrylamide are examples of monomers containing a (-CONH)- group. Suitable co-reactive monomers containing amine groups include allylamine, 2-aminoethyl acrylate and 2-aminoethyl methacrylate. Other monomers that can be suitably used in the coreactive polymer particles are those that can be copolymerized with the coreactive monomer. In general, the monomers previously described as useful in making oxazoline-modified polymers are also useful in making co-reactive polymers. In fact, in preferred embodiments of the invention where the pendant oxazoline groups and the co-reactive groups are present in different parts of the latex particles (i.e. different polymer backbones), the polymer backbone of the co-reactive polymer is It is often desirable to "match" that of the oxazoline-modified polymer. In other words, in this embodiment it is desirable to use the same types of polymers in the same proportions in both the co-reactive polymer and the oxazoline-modified polymer. However, dissimilar polymers can also be used in the preparation of the oxazoline modified polymers and co-reactive polymers to obtain the desired specific properties. As with oxazoline-modified polymers, polymers with pendant co-reactive groups generally contain only small amounts of repeating units derived from co-reactive monomers. Generally, the co-reactive monomer is used in an amount sufficient to impart the desired self-curing properties to the latex composition, and the other monomers impart properties typically associated with polymers prepared from such monomers. used for. Generally, when the pendant co-reactive group is present on a different part of the latex particle than the pendant oxazoline group, the co-reactive monomer will be 0.1 to 50% by weight of the monomers used to make the co-reactive polymer. Preferably 0.1-20% by weight, most preferably 1-10
Makes up % by weight. When the pendant co-reactive groups are present on different parts of the polymer particles, the co-reactive polymer particles and the oxazoline polymer particles are conveniently prepared by emulsion polymerization techniques. These latexes are conveniently prepared by conventional emulsion polymerization techniques in an aqueous medium using conventional additives. Thus, for example, the monomer charge that one desires to use for an oxazoline-modified latex may be combined with conventional anionic and/or nonionic emulsifiers (e.g. n
- potassium dodecylsulfonate, sodium isooctobenzenesulfonate, sodium laurate, and nonylphenol ether of polyethylene glycol) dispersed in a stirred aqueous medium containing 0.5 to 5% by weight (based on the filled monomers);
The resulting aqueous dispersion is then polymerized. Conventional emulsion polymerization catalysts can be used in the latex polymerization, common practices include peroxides, persulfates, and azo compounds. Suitable examples are sodium persulfate, potassium persulfate, ammonium persulfate, hydrogen peroxide, and azodiisobutyldiamide. Catalysts such as redox catalysts activated in the aqueous phase, for example by water-soluble reducing agents, are also suitable. The type and amount of catalyst and the particular polymerization conditions used typically depend primarily on the other (ie, non-co-reactive and non-oxazoline) monomers used. Polymerization conditions are generally selected to optimize polymerization of such other monomers. Typically, the catalyst is used in a catalytic amount, e.g.
Used in amounts of % by weight. Generally, polymerization is −10~
It is carried out at a temperature in the range of 110°C (preferably in the range of 50 to 90°C). Since the oxazoline group of the oxazoline monomer hydrolyzes or reacts with other monomers at high or low pH, the polymerization is conducted at a pH that minimizes this hydrolysis or reaction. Typically a pH of 3-11, preferably 6-11
Use a PH of 11. More preferably a pH of 7 to 10
is suitable. Polymerization can be carried out continuously, semi-continuously or batchwise. Similarly, the customary chain transfer agents such as n-dodecylmercaptan, bromoform and carbon tetrachloride can be used in the customary manner in the above polymerizations for controlling the molecular weight of the resulting polymer. Typically, when such chain transfer agents are used, they are
It is used in amounts ranging from 0.01 to 10 (preferably 0.1 to 5)% by weight. Again, the amount of chain transfer agent used will depend somewhat on the particular chain transfer agent used and the particular monomers being polymerized. Suitable latex polymerization methods are described, for example, in U.S. Pat.
No. 4325856, No. 4001163, No. 3513121, No. 3575913, No. 3634298, No. 2399684,
Same No. 2790735, Same No. 2880189, and Same No.
Described in No. 2949386. When the co-reactive monomer is a monomer containing a pendant weak acid group, such as a carboxyl group, the polymerization is carried out under sufficiently acidic conditions to promote polymerization of the weak acid co-reactive monomer with the other monomers used. is advantageous. Preferably, the pH is maintained between 1 and 6, more preferably between 1 and 4. After the polymerization reaction, the pH of the aqueous phase is then adjusted with a base, typically from 7.5 to
The pH was adjusted to 9 to prevent the oxazoline rings in the oxazoline-modified latex from being hydrolyzed during the next blending operation. The curable latex composition of the present invention comprises an oxazoline-modified latex and a coreactive latex,
Advantageously, they are manufactured by simply blending the respective latexes in the desired proportions. in general,
The relative ratio of the oxazoline-modified latex to the co-reactive latex is such that the self-curing latex produced is 0.05 to 20 equivalents, preferably 0.2 to 5 equivalents, more preferably 0.5 to 2 equivalents per equivalent of oxazoline group.
It is selected to contain an equivalent amount of acid groups. Also, better water and solvent resistance and greater tensile strength are generally observed when the latex composition contains approximately comparable amounts of oxazoline-modified polymer particles and co-reactive polymer particles. Preferably, the latex is
It contains 0.1 to 10, more preferably 0.2 to 5, most preferably 0.40 to 2.5 oxazoline modified polymer particles. Such blending operations are advantageously carried out at room temperature with mild stirring. The product is an aqueous dispersion containing discrete particles of oxazoline modified polymer and discrete particles of acid polymer. Advantageously, the particle size of the oxazoline-modified polymer and the co-reactive polymer and their respective particle size distributions are selected such that these particles tend to pack well together to form a dense cohesive film. It will be done. These particles may all be of relatively uniform size, or they may be of different sizes such that packing of these particles together during film formation is enhanced. good. The latices of the present invention, where both the pendant co-reactive weak acid groups and the pendant oxazoline groups are present in the same latex particle, are advantageously prepared by a two-step emulsion polymerization process. In the first stage of polymerization, a first monomer mixture consisting of an addition-polymerizable co-reactive weak acid monomer and at least one other monomer copolymerizable therewith is polymerized. Such first polymerization step is conveniently carried out using substantially conventional emulsion polymerization techniques in an aqueous medium containing conventional additives as described above. Typically, the aqueous phase contains 0.5 to 5% by weight (based on monomer charge) of conventional nonionic or anionic emulsifiers. Conventional emulsion polymerization catalysts, such as those described above, can be used in the latex polymerization described above. As mentioned above, when the co-reactive monomer is a monomer containing a pendant weak acid group, such as a carboxyl group, as described below,
The polymerization is advantageously carried out under sufficiently acidic conditions to promote copolymerization of the weak acid co-reactive monomer with the other monomers used. In such a case,
The PH is preferably between 1 and 6, more preferably between 1 and 4. Polymerization can be carried out continuously, semi-continuously or batchwise. Similarly, conventional chain transfer agents, such as those described above, can be used in conventional methods and amounts in the first stage polymerization to control the molecular weight of the resulting polymer. The preferred co-reactive weak acid monomer used in polymerizing the pendant oxazoline group in the same latex particle as the pendant co-reactive group is a pendant co-reactive weak acid group capable of reacting with the oxazoline group to form a covalent bond. It is a monomer containing. It is understood that the reaction of such co-reactive weak acid groups with the oxazoline group typically, but not necessarily, opens the oxazoline ring. Particularly preferred for the two-step polymerization process according to the invention are ethylenically unsaturated monomers containing pendant weak acid groups (including acid anhydride groups). Examples of such co-reactive weak acid monomers containing carboxylic acid groups include itaconic acid, acrylic acid, methacrylic acid, fumaric acid, maleic acid, vinylbenzoic acid, and isopropenylbenzoic acid. Most preferred are acrylic acid, methacrylic acid, fumaric acid, itaconic acid and maleic acid. Maleic anhydride is an example of a suitable monomer containing an acid anhydride group. In addition to the co-reactive weak acid monomer, the first monomer mixture also includes at least one other monomer that is not a co-reactive monomer and is copolymerizable with the co-reactive monomer. A wide variety of addition polymerizable monomers that can be copolymerized with the co-reactive monomers have been described above. The proportions of monomers used in the first monomer mixture can vary depending on the particular end use of the composition. Typically, however, co-reactive weak acid groups are used in relatively small amounts, such as from 0.1 to 20%, preferably from 1 to 10%, by weight of the monomers. Generally, the co-reactive weak acid monomer is used primarily to impart the desired self-curing properties to the latex composition, while other monomers are used to impart other desired properties to the composition. For example, preferred acids/
In oxazoline-modified styrene/butadiene latexes, the oxazoline-modified polymer advantageously exhibits properties similar to those normally associated with styrene/butadiene polymers, and the co-reactive weak acid monomer contributes little to the polymer other than curing properties. It is noted that weak acid-containing polymers also exhibit increased colloidal stability. Once the polymerization of the first monomer mixture is complete, the pH of the resulting co-reactive latex is such that, if desired, the oxazoline ring does not significantly react or hydrolyze during the subsequent polymerization of the second monomer mixture containing the oxazoline monomer. Adjust to a high enough range to make it so. Typically, the pH is adjusted to 3-11, preferably 6-11, more preferably 7-10. Advantageously, any conventional water-soluble alkaline substance such as ammonium hydroxide, sodium bicarbonate or sodium hydroxide is used to raise the PH in the aqueous phase. A second monomer mixture consisting of an oxazoline monomer and at least one other addition polymerizable monomer that is neither a co-reactive monomer nor an oxazoline and that is capable of reacting with the oxazoline monomer is added to the co-reactive latex. The "other" copolymerizable monomer and oxazoline monomer are as described above. A second monomer mixture is added to the co-reactive latex under conditions such that these monomers polymerize into or around the co-reactive latex particles. The general conditions used are as described above, with the exception that the pH of the aqueous phase is adjusted to the above range (i.e., to a range sufficient to prevent substantial reaction or hydrolysis of the oxazoline monomer) if necessary during the polymerization reaction. That's right. If necessary or desired, additional amounts of aqueous phase emulsifiers, catalysts, initiators, etc. can be added to the co-reactive latex prior to or concurrently with the addition of the second monomer mixture to accelerate its polymerization. The second stage of polymerization can be carried out immediately after the production of the co-reactive latex. Alternatively, the co-reactive latex can be made in advance and stored until the second stage polymerization is carried out. The monomers used in the first monomer mixture can be "matched" with the monomers used in the second monomer mixture, i.e., the monomers used in the first monomer mixture can be
It is possible and often desirable to use the same or substantially similar monomers in the same or substantially similar proportions in both monomer mixtures. For example, if styrene, butadiene and acrylic acid were used in the first monomer mixture, a second monomer mixture comprising styrene, butadiene and oxazoline monomers could be used to match the first and second monomer mixtures. . Of course, matching the skeletons of the first and second monomer mixtures is not essential or always preferred in the practice of this invention.
More generally, the selection of the other monomers in the first and second monomer mixtures is such that the resulting latex has the desired physical and chemical properties. The proportions of monomers used in the second monomer mixture can vary depending on the particular end use of the composition. Typically, however, oxazolines are used in relatively small amounts, such as from 0.1 to 20%, preferably from 1 to 10%, by weight of the monomers. Generally, oxazoline monomers are used to impart self-curing properties to the latex, and other monomers are used to impart other desired properties to the latex. Advantageously, the second monomer mixture contains 1 mole of co-reactive monomer used in the first monomer mixture.
It contains 0.05 to 20 moles, preferably 0.2 to 5 moles, more preferably 0.05 to 2 moles of oxazoline monomer. Most preferably, the amount of oxazoline monomer used is substantially equal on a molar basis to the amount of acid monomer used. After polymerization of the second monomer mixture, a curable latex mixture is obtained. Such a composition is (a)
It consists of discrete polymer particles produced by addition polymerization of monomers consisting of a co-reactive monomer, (b) the aforementioned oxazoline monomer, and (c) at least one other addition-polymerizable monomer. If the other monomers in the first monomer mixture are different from the other monomers used in the second monomer mixture, the resulting latex particles contain, in addition to the oxazoline monomer and the co-reactive monomer, at least two other polymerizable monomers. It is manufactured from monomers. While not being bound by theory, the polymer particles in the latex produced by this method are such that the polymer formed in the second polymer mixture envelops the polymer formed from the first monomer mixture in a carcelular manner. It is believed to be a structured latex that contains or interpenetrates the structure. However, it is recognized that some amount of graft or block copolymer may be formed during the polymerization of this second monomer mixture. The precise polymeric structure of the polymer particles is not considered important to the invention. The essential feature of this polymer particle is that such particles contain both pendant co-reactive groups and pendant oxazoline groups. Advantageously, the polymer particles have a particle size distribution such that during film formation, the particles are packed relatively closely together to form a cohesive film. The curable latex compositions of this invention can be used in a variety of applications including paper coating compositions, adhesives, binders, and fibrous nonwoven compositions. The latex of the present invention can be prepared by layering the latex on a desired substrate, then dehydrating the latex,
and by curing the dehydrated polymer,
Can be used as an adhesive, film or binder. The dehydration step can be carried out by simply evaporating the aqueous phase under room temperature conditions. Alternatively, elevated temperatures (i.e. 50-165°C) can be used to effect dehydration. Curing of the polymer can likewise be carried out at room temperature. Such room temperature curing depends on the particular polymer used, the amount of oxazoline groups and co-reactive groups in the polymer,
This can take place over a period of several hours to several days, depending on factors such as the thickness of the film adhesive or binder layer and the amount of cross-linking desired. Curing also preferably heats the polymer to 105-165°C, more preferably 135°C.
This can also be done by short-term heating to ~150°C. The drying and curing points described above do not need to be separate steps and can be performed simultaneously if desired. The following Example 1 is intended to illustrate aspects of the invention where the co-reactive group and the oxazoline group are present in different parts of the latex particles.
All parts and percentages are by weight unless otherwise specified. Example 1 Blended Latex Composition A Preparation of Carboxylated Latex In a ¹ gallon jacketed reactor equipped with an FMI experimental pump to deliver the monomer and aqueous feeds, 590 g of water, 7 g of 1% Activated pentansodium diethylenetriamine pentaacetate aqueous solution and 24.4 g of 29% solids seed latex were added. Seed latex is approx.
It contained polystyrene particles with a volume average particle size of 0.0275 μm (275 Å). The reactor was purged with nitrogen and heated to 90°C. Then over a period of 3 hours, a monomer stream containing 455 g of butyl acrylate, 211 g of styrene and 28 g of acrylic acid was added. 245 g deionized water,
15.56g of 45% active surfactant aqueous solution, 14g of
A 10% aqueous sodium hydroxide solution and 4.9 g of sodium persulfate were added. After addition of the aqueous stream of monomer, the reaction mixture was heated at 90° C. for an additional hour and then cooled. The product is 65/
It was a 44.8% solids latex of butyl acrylate/styrene/acrylic acid polymer in a weight ratio of 31/4. B Oxazoline Modified Latex In a 0.0038 m ³ (1 gallon) jacketed reactor, 146 parts deionized water, 0.01 part 0.1% pentansodium diethylenetriamine pentaacetate in water, 5.0 parts Dresinate TM 214 surfactant (Hercules Inc.) (commercially available from ) and 0.5 part sodium persulfate were added. The reactor was stirred and purged with nitrogen. Then, in this stirring reactor,
25 parts styrene, 5 parts 2-isopropenyl-2
-oxazoline (IPO) and 0.5 part of t-dodecylmercaptan was added.
Then 70 parts of butadiene were added and the mixture was polymerized at 60° C. for 8 hours. The reactor was then opened and 0.5 part of sodium dimethyldithiocarbamate was added. This latex was then steam distilled to remove unreacted monomers. The resulting latex contained 33.5% solids and had polymer particles consisting of a butadiene/styrene/IPO terpolymer in a weight ratio of 70/25/5. In the table below, this oxazoline-modified latex is referred to as latex No. 1. Amount of butadiene/styrene/IPO and t-
Oxazoline-modified latexes Nos. 2, 3, and 4 and comparative latex No. C were prepared using the general method used to prepare Latex No. 1, except that the amount of dodecyl mercaptan was varied as shown in the table below. -1, C-2 and C-3 were produced. No sodium dimethyl dithiocarbamate was added to the latex containing 50 parts of butadiene. These latexes (with the exception of the comparative latexes, of course) are ingredients that are blended to produce latexes according to the invention, and are not themselves compositions of the invention.

[Table] Equal weight (solid basis) IPO modified latex No.1
A self-curing latex composition was prepared by stirring together the above carboxylated latex at room temperature. IPO modified latex and carboxylated latex were compatible at all ratios. The resulting blend is referred to as Latex Composition No. 1 in the table below. Similarly, IPO
Latex Composition No. 1 was prepared by mixing modified latexes Nos. 2, 3, and 4 and comparative latexes Nos. C-1, C-2, and C-3 on an equal weight solids basis with the carboxylated latex described above. 2,
3 and 4 and comparative latex composition No.C-
1, C-2 and C-3 were prepared. Sample No. 4 was carboxylated latex alone. Multilayer films from Latex Compositions Nos. 1 to 4 and Comparative Latex Compositions Nos. C-1 to C-3 were pulled down onto a Teflon-coated steel plate with a thickness of 0.51 mm (20 mils) and the films were then transparentized. It was prepared by drying at room temperature until Next, peel off the transparent film from the steel plate and leave it at room temperature for about 20 minutes.
Dry for 24 hours. Then some of the produced film is 80
C., 120.degree. C., or 150.degree. C. for 5 minutes. The resulting film was then cut into 13 mm (0.5 inch) wide strips and tested for elongation at break and tensile strength on an Instron tensile tester. Also,
A similar sample was immersed in a 0.5% surfactant aqueous solution for 5 minutes, and the wet film was tested for elongation at break and tensile strength using the Instron tensile test.
These results are shown in the table below. Elongation values are shown in %, tensile strength is in megapascals (MPa)
It is shown.

【table】

TABLE As can be seen from the table, the latex compositions of the present invention generally formed films with higher tensile strength and slightly lower elongation than the comparative latex compositions. The data presented in the table clearly illustrate the improved water resistance exhibited by the latex compositions of the present invention. Films made from the comparative latex compositions exhibited a tensile strength decrease of about 30-70% when wet. In contrast, the latex compositions of the present invention typically exhibit only about a 10-20% reduction in tensile strength. It is therefore clear that films made from latex compositions of the present invention are significantly less sensitive to water than films made from comparative latex compositions.
Films made from the latex compositions of the present invention also exhibit an excellent combination of good elongation and high tensile strength in both dry and wet samples. To measure the degree of cross-linking and solvent resistance,
The swelling index and gel % of the films cured at room temperature, 100°C, 120°C and 150°C were determined as follows. Multiple film samples were made from each of latex compositions No. 1 and C-1 using a 0.51 mm (0.020 inch) casting rod. Each film was dried until transparent and peeled off as a continuous film. One film was tested without curing, and the other films were tested at 100°C, respectively.
Tested after curing for 5 minutes at 120°C and 150°C. The test film was placed in a centrifuge tube.
30g of toluene was put into this tube. The tube was sealed and shaken vigorously for 90 minutes. The tube was then centrifuged at approximately 18,000-19,200 rpm for 1 hour. The toluene was then removed and the remaining wet gel was weighed. The gel was then dried in a vacuum oven to constant weight. Gel % and swelling index are each calculated from the following formulas. Gel % = weight of dry gel/weight of film sample x 100% Swelling index = weight of wet gel - weight of dry gel/weight of dry gel x 100% The results obtained are shown in the following table.

Table: As can be seen from the table, films made from latexes of the present invention showed greatly increased solvent resistance and a greater proportion of insoluble materials compared to the comparative samples from latex compositions No. 2, 3 and 4. The produced films were similarly tested and also showed improved solvent resistance and a greater proportion of insoluble material compared to the control. Examples 2-5 below illustrate an aspect of the invention where the co-reactive group and the oxazoline group are present in the same latex particle. Example 2 Two-Stage Polymerization Latex Composition In a ¹ gallon jacketed reactor equipped with a laboratory pump to deliver the monomer and aqueous feed, 593 g deionized water, 7 g 1% active pentansodium diethylenetriamine. An aqueous pentaacetate solution and 21.9 g of a 32% solids seed latex (containing polystyrene particles with a volume average particle size of about 0.0263 μm) were added. The reactor was purged with nitrogen and heated to 90°C.
Then over a period of 3 hours, 455 g of butyl acrylate, 217 g of styrene, 28 g of acrylic acid,
and 3.8 g of 55% active divinylbenzene were added. Starting simultaneously with the start of monomer flow, 245 g of deionized water, 15.56 g of 45% active surfactant in water, 14 g of 10% sodium hydroxide in water and 4.9 g of sodium persulfate were added over 4 hours. Ta. After addition of monomer and aqueous liquid stream, the reaction mixture was heated at 90° C. for an additional hour and then cooled. Product is 65/31/4/0.3% by weight
It was a 45% solids latex of a polymer of butyl acrylate/styrene/acrylic acid/divinylbenzene in the ratio. A 1244.0 g portion of the co-reactive latex produced was combined with 0.0038 m ³ of 100 g of water and enough ammonium hydroxide to raise the pH from 3.9 to 8.7.
(1 gallon) stainless steel reactor. The reactor was then purged with nitrogen and a monomer mixture consisting of 14 g of 2-isopropenyl-2-oxazoline, 91 g of butyl acrylate, and 35 g of styrene was added. 171g dehydrated ionized water and 0.7
g of sodium persulfate was also added. The resulting mixture was then polymerized at 60°C for 8 hours before being cooled. The resulting latex contained polymer particles with both pendant acid groups and pendant oxazoline groups as determined by infrared spectroscopy. The resulting latex was thickened with a small amount of sodium polyacrylate to reduce the thickness of this latex to 0.51 mm (20
mil) thick film was casted onto a Teflon coated steel plate using a 0.51 mm (20 mil) thick film rod. The film was dried at room temperature until clear, then removed from the steel plate and dried for an additional approximately 24 hours at room temperature. The air-dried films were then cured for 5 minutes in an oven set at various curing temperatures listed in the table above. The cured film was then cut into 13 mm (0.5 inch) wide strips and tested on an Instron testing machine to determine elongation and tensile strength at break. Similar cured films were immersed in an excess amount of an aqueous solution containing 0.5% Aerosol OT surfactant for 5 minutes and then measured for elongation and tensile strength at break. For comparison,
Samples of carboxylated latexes containing no suspended oxazoline groups were formed into films and tested as described above. The results obtained from the test of this comparative example are shown in the table as sample No. C-1. The results obtained for the film produced from the latex of the present invention are shown in the table as Sample No. 1. Tensile strength values are given in MPa.

【table】

TABLE As can be seen from the table, the latex of the present invention produced films with higher tensile strength than films made from the control latex.
Even more strongly, the films of the present invention do not suffer significant damage when the films are immersed in surfactant-containing water. In fact, at high curing temperatures, wetting the film increases its tensile strength.
In contrast, the control sample significantly loses tensile strength upon immersion in the surfactant solution. Example 3 In this example, a styrene/butadiene/fumaric acid terpolymer (weight ratio of 57.6/40.5/1.9)
A co-reactive latex containing (51% solids) was used as the starting material. A 1584g portion of this latex is 0.0038m ³ (1
gallons) into a stainless steel reactor. A sufficient amount of 28% aqueous ammonium hydroxide was added to the latex to raise the pH to approximately 8.5. then 198
g of deionized water, 2 g of 1% active sodium diethylenetriamine pentaacetate solution, 1 g of sodium persulfate, 20 g of 2-isopropenyl-
2-oxazoline, 99 g styrene, and 4 g
of carbon tetrachloride was added. The reactor was then purged with nitrogen and 81 g of butadiene was added. The reaction mixture was then heated to 60°C for 80 minutes. The latex was then steam distilled to remove unreacted monomers. The resulting latex contained particles with both pendant reactive groups and pendant oxazoline groups as determined by infrared spectroscopy. A film was made from the resulting latex and cured as described in Example 2 above. The tensile properties of the resulting film were tested as described in Example 2. The results are shown in the table below. For comparison, a portion of the co-reactive latex that was not modified with the oxazoline polymer was prepared in Example 2.
The film was formed into a film, cured and tested as described in . The results are shown in the following table as sample No. 2.

TABLE This table shows that the dry tensile strength of the carboxylated IPO modified latex is substantially equal to that of the dry carboxylated latex. However, when evaluating wet tensile strength, films made from the latex of the present invention clearly outperform the comparative samples. Example 4 In this example, a styrene/butadiene/acrylic acid terpolymer with a ratio of 58/38/4 was prepared.
A 48.6% solids latex was used as the co-reactive starting material. A 1646g portion of this latex is ^0.0038m3 (1
gallons) into a stainless steel reactor. A sufficient amount of 28% ammonium hydroxide in water was added to the latex to raise the pH to approximately 8.6. then 198
g deionized water, 1 g sodium persulfate, 2.0
g of 1% active sodium diethylenetetramine pentaacetate solution, 20 g of 2-isopropenyl-2-oxazoline, 96 g of styrene, and 6
g of carbon tetrachloride was added to the reactor. The reactor was then purged with nitrogen and 84 g of butadiene was added. The resulting mixture was then polymerized at 60°C for 7 hours. The resulting latex contained particles with both suspended acid groups and suspended oxazoline groups. Films were prepared from the resulting latex by the method described in Example 2 and tested for tensile properties. The results are shown in Table 1. For comparison, films were prepared from carboxylated latexes that did not contain oxazoline groups. These films were tested for tensile properties and the results are shown in the following table as Sample No. C-3.

Table: Again, the excellent tensile properties of the wet and dry films of the invention were observed. Example 5 A glass reactor immersed in a temperature-controlled water bath was charged with 359 g of deionized water, 3 g of a 1% active pentansodium diethylenetriamine pentaacetate solution, and 4.5 g of a 32% solid seed latex (containing polystyrene polymer particles). added. The reactor was purged with nitrogen and heated to 83°C. then 90 g of butyl acrylate over 1 hour;
A first monomer stream containing 53.75 g methyl methacrylate and 5.0 g acrylic acid was added. After the first monomer addition, the reactor was held at approximately 83°C for 15 minutes. Add 3g of 28% ammonium hydroxide solution to raise the pH from 3.5 to 8.3, then add a second
monomer flow started. A second monomer stream was added over 1 hour. The second monomer stream contained 90 g of butyl acrylate, 53.75 g of methyl methacrylate, and 7.5 g of 2-isopropenyl-2-oxazoline. 90 g deionized water over 2 1/4 hours starting at the start of the first monomer addition;
An aqueous stream containing 1.5 g sodium persulfite, 0.3 g NaOH, and 3.3 g 45% active surfactant solution was also added. After addition of the first monomer stream and the aqueous stream, the reactor is held at 83°C for an additional hour;
Then it was cooled. The latex was formed into a film as in Example 2. The film was cured by heating at 125° C. for 5 minutes and tested for tensile strength and elongation as in Example 2. The results are shown in the table below. For comparison, films were produced in the same manner using the following various latexes. Sample No.C-4A Butyl acrylate/Methyl methacrylate (60/40) Sample No.C-4B Butyl acrylate/Methyl methacrylate/Acrylic acid (60/38.33/1.67) Sample No.C-4C Butyl acrylate/Methyl methacrylate Acrylate/2-isopropenyl-2-oxazoline (60/37.5/2.5) Sample No.C-4D 50:50 blend of C-4B and C-4C The tensile strength and elongation of all films were determined as described above. It was tested as follows. The results are shown in the table below.

Table: As can be seen from the data in the table, films made from the latex of the present invention exhibit the highest tensile strength in both wet and dry tests.

Claims (1)

[Scope of Claims] 1. A curable latex composition comprising a group of discrete polymer particles, the polymer portion of which contains (a) a co-reactive monomer containing a pendant group capable of reacting with an oxazoline group to form a covalent bond; and (b) general formula [wherein R ¹ is an acyclic organic group having addition polymerizable unsaturation; each R ² is independently hydrogen, halogen, or an inert substituted organic group; n is 1 or 2]; and (c) at least one other addition-polymerizable monomer that does not contain a co-reactive group or an oxazoline group (provided that the oxazoline group and the co-reactive group are suspended). A curable latex composition characterized by: 2. The composition of claim 1, wherein both (a) the pendant co-reactive groups and (b) the pendant oxazoline groups are present in the same latex particle in at least a portion of the latex particles. . 3. (a) the pendant co-reactive group is present on one portion of the latex particles; and (b) the pendant oxazoline group is present on a second separate portion of the latex particles. Composition according to item 1. 4. The composition according to claim 1, wherein the co-reactive group is a weak acid, aliphatic alcohol, aromatic alcohol, amine or amide group. 5. The composition according to claim 1, wherein the co-reactive monomer is an α,β-ethylenically unsaturated carboxylic acid or an acid anhydride. 6. The composition according to claim 1, wherein the oxazoline is 2-isopropenyl-2-oxazoline. 7. A process for producing a latex consisting of a separate group of particles containing both pendant co-reactive weak acid groups and pendant oxazoline groups, comprising the following steps: (a) addition-polymerizable monomers containing pendant weak acid groups; A first monomer mixture consisting of this weak acid monomer and at least one other addition-polymerizable monomer that can be copolymerized with 1 to 6
producing a latex comprising particles of a polymer containing suspended weak acid groups by polymerization at a pH in the range of
Next, (b) the pH of the produced latex is adjusted to a value at which the addition-polymerizable oxazoline does not substantially react or hydrolyze under conditions suitable for polymerization, and (c) this latex is treated with (1) the general formula [wherein R ¹ is an acyclic organic group with addition polymerizable unsaturation; each R ² is independently hydrogen, halogen, or an inert substituted organic group; n is 1 or 2]. (d) adding a second monomer mixture consisting of an addition polymerizable oxazoline represented by A method comprising the steps of polymerizing a monomer mixture under conditions such that a second monomer mixture is polymerized in or around polymer particles containing pendant co-reactive weak acid groups. 8 the first monomer mixture consists of an α,β-ethylenically unsaturated carboxylic acid and a monovinyl aromatic monomer or an α,β-ethylenically unsaturated carboxylic acid alkyl ester or an aliphatic conjugated diene;
8. The method of claim 7, wherein the second monomer mixture comprises an addition-polymerizable oxazoline and a monovinyl aromatic monomer or an .alpha.,.beta.-ethylenically unsaturated carboxylic acid alkyl ester or an aliphatic conjugated diene. 9. The method according to claim 7, wherein the oxazoline is 2-isopropenyl-2-oxazoline. 10 Claim 7 which adjusts the PH to 7 to 11
The method described in section. 11 the second monomer mixture per mole of co-reactive monomer used in the first monomer mixture
8. The method of claim 7, comprising 0.5 to 2 moles of oxazoline. 12. The method of claim 8, wherein the co-reactive monomer is acrylic acid, methacrylic acid, itaconic acid or fumaric acid and the oxazoline is 2-isopropenyl-2-oxazoline.