FI86309C - VAERME- OCH LJUSBESTAENDIGA LATEXER BESTAOENDE AV IN I VARANDRA TRAENGANDE POLYMERNAET. - Google Patents

Description

The present invention relates to stable water-containing latices having improved heat and light resistance and good mechanical properties. 1 86309 Heat and light resistant latexes consisting of interpenetrating polymer networks.

Aqueous dispersions of polymers, referred to in the art as latices, are generally known to be useful, both alone and in various formulations, as coatings and impregnating agents. A wide variety of latices with different homopolymer or copolymer compositions (e.g. styrene-butadiene copolymers, acrylic homopolymers and copolymers, vinylidene chloride homopolymers and copolymers and copolymers, etc.) have been accurately quantified and quantified, etc.) with a view to their end uses. For example, aqueous copolymer latices obtained from aromatic monovinylidene monomers such as styrene; diolefins such as Buta-20 diene; and ethylenically monounsaturated carboxylic acids such as acrylic acid; as a result of emulsion polymerization, are known to be particularly useful as film-forming binders in pigments used in paper coating; examples are U.S. Patent Nos. 3,399,080 and 3,404,116.

Unfortunately, in the design of latexes in which different properties are specifically combined for this purpose, complete flexibility could theoretically be considered possible (e.g. 30 of the known advantageous properties of each of the many known groups and species of addition polymerizable monomer constituents for each group or species). However, in practice, this has not proved possible due to some problematic issues. Such factors include, for example, incompatibilities between different groups and / or species of known monomeric substances, large differences in reactivity between monomeric substances, and the like.

5 It is desirable that the latex be substantially stable to heat or light decomposition or discoloration. For example, styrene-butadiene type latexes do not have good heat and light resistance. However, the incorporation of styrene and butadiene into the latexes is preferred because such latices have good elastomeric properties as well as other preferred physical properties such as advantageous elongation, tensile strength and modulus. In addition, it is often desirable to prepare flammable latexes for specific purposes. Unfortunately, conventional latexes often do not have significant resistance to decomposition by heat and light, and in particular to discoloration.

The aforementioned problems in the field of hours have been attempted in the past to overcome or at least minimize these problems. For example, U.S. Patent No. 4,002,801 discloses that some reactive monomers that do not readily copolymerize with other monomers can nevertheless be incorporated into the latex particle by encapsulating or "overpolymerizing" the desired homopolymer or copolymer with the desired reactive copolymers. Unfortunately, such an improvement is not without its drawbacks or limitations. For example, only certain types of encapsulating polymers are useful, and there is an upper limit to the amount of polymer solids that can be prepared in this manner without flocculation or precipitation of the latex.

As disclosed in U.S. Patent No. 4,325,856, aqueous copolymer latices are prepared which contain colloidally dispersed, substantially spherical copolymer particles consisting of a core portion having a predominant hydrophobic orientation and a relatively hydrophilic polymeric moiety. . Although such latexes provide the desired physical properties of the various copolymerizable ingredients, the physical properties of such latexes are not very balanced.

Thus, it would be highly desirable to provide better latices as well as a process for their preparation by which polymers which provide the desired combinations of properties in said latexes can be mixed together so as to result in the desired balance of mechanical properties.

The invention relates to a latex of interpenetrating polymer networks which is thermally and light stable and has good mechanical properties, the latex comprising a continuous phase containing a crosslinked polymer (I) network and a discontinuous phase containing polymer (II) but each inside the latex particle with a mutually indivisible, microphase. The latex is characterized in that the polymer (I) is a hydrophilic polymer having ··. 25 (1) 50 to 80% by weight of acrylate or methacrylate monomers, (2) 40 to 17.8% by weight of aromatic monovinyl monomer, (3) 8 to 2% by weight of other monomer selected from 30 groups amides derived from α, β-olefinically unsaturated carboxylic acids, and N-alkylol and N-alkoxyalkyl derivatives of these amides, and (4) 2 to 0.2% by weight of a polyvinyl crosslinking monomer; and 35 the polymer (II) is a hydrophobic polymer having 4 86309 (1) 50 to 80% by weight of an aromatic monovinyl monomer or vinyl halide monomer and (2) 50 to 20% by weight of an open-chain conjugated diene, wherein the hydrophobic polymer moiety is emulsion polymerized in said crosslinked, hydrophilic polymer network.

By "good physical properties" is meant that the physical properties, such as elongation, tensile strength, and modulus, are close to those provided by a latex composed primarily of a hydrophobic polymer phase. In other words, the specific properties of IPN are the result of a combination of the specific properties of each of the different polymer components. The physical properties of IPN 15 are superior to those of blends of latexes, each of which gives the blend stability and good physical properties.

The systematically constructed latexes of this invention can be broadly described as interpenetrating polymer networks (IPNs) based on the two types of polymers, each in the form of a network. For purposes of this invention, the morphology of each IPN latex-25 particle consists of substantially microphases formed within the continuous hydrophilic polymer phase that are essentially formed by a hydrophobic polymer.

The IPN latexes of this invention can be used in applications where mechanically resistant latexes have been used in the past and where heat resistance and non-flammability are desirable. Such applications include paper coating materials, carpet backing adhesive, composite papers, fabric coating materials, metal mesh reinforced kraft laminates, cement applications and other known applications.

A network of interpenetrating polymers (IPN) is a unique type of polymer blend that can be defined as a combination of two polymers, mainly in the form of a network. The compositions of this invention are prepared by incorporating monovinyl monomer or monomers into an existing, or at least partially existing, crosslinked polymer network (polymer I) and optionally, and preferably, a conjugated diene as a crosslinking agent (Phase II mixture). preferably by swelling and then polymerizing the mixture of step II in situ (while further polymerizing the polymer I network if necessary) to form a second polymer network (polymer 15 II). The second polymer network is continuous throughout the composition, and both networks are substantially chemically independent of each other. A characteristic feature of the IPNs of this invention is that the networks are induced to penetrate each other in the latex (i.e., both networks spread across wide spacings to form microphases).

The polymer I networks used in the practical applications of this invention, i.e. hydrophilic polymer networks, are generally polymer networks having excellent heat and light resistance. Such heat and light resistance is obtained for latex by polymerizing monomers which, when polymerized, form a predominantly hydrophilic polymer network.

Suitable monomers for polymerization to obtain such hydrophilic polymers include acrylate and methacrylate monomers, for example, hydroxyalkyl acrylates in which the alkyl group contains from two to about four carbon atoms, such as 2-hydroxyethyl acrylate or 3-hydroxypropyl acrylate; alkyl acrylates, of which the alkyl group contains from one to about eighteen carbon atoms, such as methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, (2-ethylhexyl) acrylate, etc .; and alkyl methacrylates such as methyl 5-methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate and other similar alkyl methacrylates.

Other monomers which can be advantageously copolymerized in the preparation of polymer I are amides derived from α, β-olefinically unsaturated carboxylic acids, such as acrylamide, methacrylamide, N-methylacrylamide, N-ethylacrylamide, N-propylacrylamide, (t-butyl) acrylamide, N- (2-ethylhexyl) acrylamide, N-methylmethacrylamide, N- (t-butyl) -15 methacrylamide, N-octylmethacrylamide, N, N-diethylacrylamide, N, N-diethylmethacrylamide and diacetoniacrylamide.

Other possible monomers include N-alkylol-20 and N-alkoxyalkyl derivatives of the above-mentioned olefinically unsaturated amides, such as N-methylolacrylamide, N-ethanolmethacrylamide, N-propanolacrylamide, N-methoxymethylacrylamide, N-methoxyacetylamide, N-methoxyethylamide , N-butoxy-ethylacrylamide, N-butoxymethylmethacrylamide and the like. Although the above monomers are preferred due to their easy availability and low cost, other structurally related polymerizable amides such as N-methylol maleic acid amide, N-methylol maleic acid amide, N-methylol-p-vinylbenzimide and diacetone acrylic amide hydroxyalkyl can be used.

Suitable monomers (2) include aromatic monovinylidene monomers, including, for example, styrene, α-methylstyrene, ortho-, meta- and para-methylstyrene, ortho-, meta- and para-ethylstyrene, o, p-dimethylstyrene. 86309 ni, o, p-diethylstyrene, o-methyl-p-isopropylstyrene, p-chlorostyrene, p-bromostyrene, o, p-dichlorostyrene and o, p-dibromostyrene.

A crosslinkable polyvinyl monomer suitable for the purposes of this invention is a di- or polyfunctional, ethylenically unsaturated monomer containing at least one α, 3-ethylenically unsaturated vinyl group. The vinyl groups contained in the crosslinking monomer may be the same groups, such as in divinylbenzene and trimethylolpropane triacrylate, or different groups, such as in allyl methacrylate, diallyl fumarate and diallyl maleate. Examples of other suitable crosslinking monomers are 1,3-butyleenidimetakrylaat 15-acetate, diethylene glycol dimethacrylate, ethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, methylene leenibisakryyliamidi, diethylene glycol, EEC leeniglykolidiakrylaatti, divinyl ether, diallyl phthalate, triethylene glycol dimethacrylate, trimethylene glycol diacrylate, 20, butylene glycol diacrylate, Pen tamethylene glycol diacrylate, glyceryl triacrylate, octylene glycol diacrylate, trimethylolpropane triacrylate and pentaerythritol tetraacrylate ester.

The polymer II phases used in the practice of this invention, i.e., the hydrophobic polymer phases, impart excellent elastomeric properties, excellent non-flammability, or other desirable mechanical properties to the latex. In particular, such properties are obtained by selecting suitable monomers that can be polymerized with suitable crosslinking monomers, such as aliphatic conjugated diene monomers.

. . Open-chain conjugated diene monomers typically contain from four to about nine carbon atoms, and such include 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, pentadiene, 2-neopentyl- β 86309 1,3-butadiene and other hydrocarbon analogs of 1,3-butadiene, as well as further substituted 1,3-butadienes such as 1-chloro-1,3-butadiene and 2-cyano-1,3-butadiene; substituted, straight-chain, conjugated pentadienes; substituted, straight-chain, conjugated hexadienes; and other straight-chain and branched conjugated dienes, preferably containing from four to about nine carbon atoms, and mixtures of these monomers. 1,3-Butadiene hydrocarbon monomers, such as those mentioned above, result in polymers that have particularly desirable properties and are therefore preferred, with 1,3-butadiene being most preferred.

Suitable monomers for use in the Phase II mixture include the aforementioned aromatic monovinylidene-15 monomers and vinyl halide or vinylidene halide dimonomers (hereinafter simply referred to as vinyl halide monomers). Suitable halides include chlorine, bromine and iodine. Particularly useful vinyl halide monomers include vinyl chloride and vinylidene chloride, and may be used singly or in combination.

When the polymer II has "soft" properties (i.e., a Tg of about 25 ° C or lower), the physical properties of the IPN, such as modulus of elasticity and tensile strength, are primarily determined by the polymer I network. However, if Polymer II is very "hard" in nature (i.e., a Tg of at least 80 ° C), the corresponding physical properties are determined by the nature of Polymer II and are substantially independent of Polymer I. In addition, IPN latexes have better heat resistance than color and flexibility comes. Such behavior is to be expected given the fact that the components of polymer I are heat-resistant and retain good flexibility. In practice, there is less discoloration with the degradation of the polymer II components, because degradation in small microphases is less pronounced than degradation in large homogeneous phases.

The polymer I networks contain (1) 50 to 80% by weight, preferably 60 to 80% by weight, of acrylate or methacrylate-5 thonomers, (2) 17.8 to 40% by weight of aromatic monovinyl monomer, ( 3) 2 to 8% by weight of another vinyl monomer, preferably an unsaturated carboxylic acid, and (4) 0.2 to 2% by weight, preferably 0.2 to 1% by weight, of a crosslinking polyvinyl monomer.

Polymer II networks contain (1) 50 to 80% by weight of aromatic monovinylidene monomers and (2) 20 to 50% by weight of open chain conjugated diene monomer or (1) 50 to 80% by weight of vinylidene halide and (2) 20% by weight of open chain conjugated diene monomer. - 50% by weight of open chain conjugated diene monomer.

Of the latex preparation models of the invention, the various polymerization steps are most preferably carried out according to conventional emulsion polymerization procedures. Thus, for example, the monomers used in each step are usually dispersed in an aqueous medium which may contain known emulsifiers (i.e. surfactants) as well as other ingredients commonly used in the art as polymerisation aids (e.g. conventional chain exchange reagents, etc.) with adequate mixing. . Said monomers are then polymerized with the aid of a conventional source to produce free radicals (i.e., conventional free radical polymerization catalysts, activating radiation, etc.).

Suitable free radical polymerization catalysts for use in the above steps include catalysts already known to promote emulsion polymerization. Some such catalysts are. . oxidizing agents such as organic peroxides (e.g.

t-butyl peroxide, cumene hydroperoxide, etc.), inorganic oxidants (e.g. hydrogen peroxide, potassium persulfate 86,309, sodium lump persulphate, ammonium persulfate, etc.) and catalysts such as redox catalysts which are activated by aqueous catalysis, for example using.

5 Such catalysts are used in an amount sufficient to effect polymerization (i.e., a catalytic amount). As a general rule, a sufficient amount is 0.01 to 5% by weight of the total amount of monomers to be polymerized. Alternatively, instead of heat and / or catalytic compounds 10, other means of generating free radicals, such as exposing the polymerization mixture to activating radiation, may be used to activate polymerization.

Suitable emulsifiers include anionic, cationic and nonionic emulsifiers commonly used in emulsion polymerization. Usually at least one anionic emulsifier is present, and one or more nonionic emulsifiers may also be present. Examples of types of anionic emulsifiers are alkylarylsulfonates, alkali metal alkyl sulfates and ras-20 wax soaps. Specific examples of these known emulsifiers are sodium (dodecylbenzenesulfonate), sodium (butylnaphthalenesulfonate), sodium laurylsulfonate, disodium (dodecyldiphenyl ether disulfonate), N-octadecyl disodium disodium sulfosuccinate Such emulsifiers can be used in varying amounts as long as sufficient emulsification is achieved to obtain dispersed polymer particles having the desired particle size and particle size distribution. As a general rule, however, it can be said that the amount preferably used is 0.01 to 5% by weight of the total amount of monomers to be polymerized. However, it should be noted that in the above-mentioned second stage polymerization, it is preferable not to add (or to add only small amounts) emulsifiers. This is desirable so that the majority of the second stage polymer is formed on or around the existing first stage polymer particles and does not initiate significant amounts of homogeneous second stage polymer particles.

In the first stage polymerization, conventional seeding procedures can be used, if desired, to facilitate the control of the polymerization and the achievement of the desired particle size and particle size distribution for the dispersed second stage copolymer particles. When seed particles are used, their amount is usually 0.1 to 1% by weight of the amount of core comonomers. In general, the diameter of such seed particles is about 10 to 20% of the diameter of the IPN latex particles to be formed. The monomer composition of the seed latex may vary as long as it does not coagulate during the formation of the phase I polymer particles.

As mentioned, conventional chain exchange reagents can be used in the practice of this invention, and it is really advantageous to do so in polymerization steps using an aliphatic conjugated diene. Examples of such conventional chain exchange reagents include bromoform, carbon tetrachloride, long chain mercaptans (e.g., lauryl mercaptan, dodecyl mercaptan, etc.), and other known chain exchange reagents. In such preferred embodiments, conventional amounts (e.g., 0.1 to 30% by weight of the total monomer charge) of such chain exchange reagents are typically used.

Other ingredients known in the art to be suitable for various specific purposes in emulsion polymerization may also be used in the above polymerization steps. For example, when the ingredients to be polymerized in a given polymerization step contain an ethylenically monounsaturated carboxylic acid monomer, the polymerization is preferably carried out under acidic conditions (for example in an aqueous medium having a pH of 2 to 7, especially 2 to 5). In such cases, the aqueous medium may contain acids i2 86309 and / or salts to provide the desired pH and optionally a buffered system. On the other hand, if the ethylenically monounsaturated carboxylic acid monomer is not used, the pH of the aqueous medium may be in the range of 5 to 10.

The following general procedure is preferably used in the preparation of the IPN latexes of this invention. The reactor used is equipped with a suitable stirrer. The reactor is also equipped with an injection device 10 suitable for adding initiators at the beginning and during the reaction. Premixing tanks are used with the reactor, which are connected to the reactor. One tank is used to premix the monomers and the other to premix the initiators and emulsifiers.

Water (most preferably distilled and treated with a chelating agent to remove metal ions) is introduced into the reactor, and nitrogen or some other inert gas is passed through it to remove oxygen. The seed polymer is preferably added to the aqueous phase.

In the first premix tank, a monomer mixture is prepared. Water, emulsifiers, initiators and possibly chelating agents are added to the second premixing tank. During the polymerization, the reactor temperature is 30 to 100 ° C, most preferably 60 to 90 ° C. Both premixes are added simultaneously or both are added continuously, and the monomers are allowed to react for less than one hour to 6 hours.

After the initial monomer charge has been allowed to react, preferably with stirring, the polymer I can be subjected to further polymerization conditions. In the same manner as in the preparation of polymer I, a monomer mixture of step II and an aqueous mixture are added to the second premix tank. The contents of both tanks are added simultaneously or continuously and allowed to react. The reactor is then cooled and the i3 86309 latex is filtered to remove any coagulate formed during the first and second polymerizations.

Such a polymerization process generally results in direct particle sizes suitable for the resulting latex. The latex particles generally have a diameter of 0.05 to 0.4, preferably 0.08 to 0.3, and most preferably about 0.1 to 0.25.

After polymerization, the solids content of the resulting water-containing polymer latex can be adjusted to the desired level by adding or removing water by distillation. Such a desired level for the content of polymeric solids is generally 30 to 65% by weight of the total weight of the latex.

Preferred IPN latexes contain 20 to 90% by weight, most preferably 25 to 75% by weight, of polymer I and 10 to 80% by weight, most preferably 25 to 75% by weight of polymer II. It is essential for the formation of IPN latexes that polymer I is one in which hydrophilicity is predominant. Polymer I, in which hydrophobicity predominates, tends to act as a seed encapsulated within hydrophilic polymers, resulting in an undesirable core-shell structure. It is also desirable for polymer I to form a more continuous phase of the IPN. This guarantees good heat and light resistance for the resulting IPN latex. Although the polymer II network is preferably a more discontinuous phase (i.e., a smaller microphase), it forms a network that provides the desired balance of mechanical properties.

The tensile strength of IPN latexes is approximately independent of the amount of polymer I and polymer II. However, the tensile strength of IPN having less than 30% by weight of polymer I and more than 70% by weight of polymer II in the composition changes as the amount of polymer II increases. This suggests that after 35 of these points, the polymer phase II is more continuous.

i4 86309

Due to the two independently continuous microphases, the compatibility of the polymers in IPN latexes is unique. Microphases are not susceptible to complete phase separation as the latex heats up. However, depending on the amount of each polymer phase, the latex may have two separate but intermediate, Tg.

In addition, it is sometimes desirable for small amounts of some known additives to be included in the latex. Typical examples of such additives are pin-10 active substances, bactericides (e.g. formaldehyde), neutralizing agents, antifoams, etc. Such additives may be included in the latices of the invention in a conventional manner and at any suitable stage in the preparation of the latices.

The aqueous IPN latexes of this invention are suitable for use in a variety of applications, such as carpet backing adhesives, binders in paper coating formulas, asbestos binders, adhesives for bonding various types of substrates such as loose films and fibrous materials, and film formers. in roads (e.g. paints, etc.) and the like. Latexes are used in the above applications following standard procedures in each of the various fields. The latices used to make the films 25 can be cured at fairly high temperatures. The resistance of the above-mentioned products resulting from the uses of the IPN latexes of this invention (e.g., by heat and light) to degradation and / or discoloration is significantly better than that of similar products using conventional latexes made from similar monomers.

The following example is intended to illustrate the invention and not to limit its scope. All proportions and percentages in the example are parts by weight and percentages in the example, unless otherwise indicated.

is 86309

Example 1

A jacketed stainless steel reactor was charged with 944.76 g of deionized water, 36 g of a 1% solution of the chelating agent, and 38.8 g of a 30.8% polystyrene seed polymer having an average particle diameter of 280 A. The reactor was deoxygenated with nitrogen and heated to 90 ° C with stirring.

The monomer mixture contained 780 g of butyl acrylate 10 (65 parts), 372 g of styrene (31 parts), 48 g of acrylic acid (4 parts) and 2.4 g of allyl methacrylate (0.2 parts). This monomer mixture was added to the reactor continuously for 3 hours at a rate of 400.8 g / h.

The aqueous mixture consisted of 480 g of deionized water, 26.6 g of 45% surfactant, 18 g of 10% sodium hydroxide solution and 8.4 g of sodium persulfate. This aqueous mixture was added to the reactor simultaneously with the addition of the monomer mixture continuously for 4 hours at a rate of 20,133.35 g / h.

The mixture was allowed to cool for an additional hour after all the ingredients had been added to the reactor. The resulting product had a solids content of 44.9% and a pH of 3.6, very little monomer-25 (0.05 g residue) and an average particle diameter of 1310 A.

A reactor as described above was charged with 681.96 g of deionized water and 846 g of the polymer blend described above. The mixture was deoxygenated with nitrogen and heated to 90 ° C with stirring.

The monomer mixture contained 420 g of styrene and 420 g of butadiene. This mixture was added to the reactor continuously for 2.8 hours at a rate of 300 g / h.

The aqueous mixture consisted of 345.6 g of deionized water, 19.2 g of 45% surfactant, i6 86309, 12.96 g of 10% sodium hydroxide solution and 6 g of sodium persulfate.

The mixture was allowed to cool for an additional hour after all the ingredients had been added to the reactor. The resulting product had a solids content of 44.65% and a pH of 3.4, very little monomer remaining (0.33 g residue), and had a mean particle diameter of 1895 A.

Claims (3)

A latex consisting of interpenetrating polymer networks which is thermally and light stable and has good mechanical properties, wherein the latex comprises a continuous phase containing a crosslinked polymer (I) network and a discontinuous but containing polymer (II) but within each latex particle polymer, I, characterized in that the polymer (I) is a hydrophilic polymer with (1) 50 to 80% by weight of acrylate or methacrylate monomers, (2) 40 to 17.8% by weight of aromatic monovinyl mono- merium, 15 (3) 8-2% by weight of another monomer selected from the group consisting of amides derived from α, β-olefinically unsaturated carboxylic acids, and N-alkylol and N-alkoxyalkyl derivatives of these amides, and (4) 2 - 0.2% by weight of polyvinyl crosslinking mono-20 mer; and polymer (II) is a hydrophobic polymer having (1) 50 to 80% by weight of an aromatic monovinyl monomer or vinyl halide monomer and (2) 50 to 20% by weight of an open-chain conjugated diene, wherein the hydrophobic polymer moiety is an emulsion polymer. in said crosslinked, hydrophilic polymer network. Latex according to Claim 1, characterized in that it contains from 20 to 90% by weight of hydrophilic polymer network and from 10 to 80% by weight of hydrophobic polymer part. Latex according to Claim 1, characterized in that it contains 25 to 75% by weight of hydrophilic polymer network and 25 to 75% by weight of hydrophobic polymer part. is 86309