JPS6030698B2 - acrylic resin composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to improved thermoplastic acrylic resin compositions.

More specifically, the present invention relates to a thermoplastic acrylic resin composition with excellent solvent resistance and fluidity. Acrylic resin is widely used both indoors and outdoors due to its excellent transparency, weather resistance, beautiful appearance, and ease of molding.

However, when exposed to certain types of solvents, crazes and cracks may occur, especially when internal stress or external stress is applied, and improvements have been desired. For improving solvent resistance, for example, a method of incorporating acrylic or methacrylic oligomers (Special Publication No. 49-131241), a method of copolymerizing certain acrylic or methacrylic monomers (Akira Hakama Seki) Kyu-7792 Publication and Tokusekki Publication No. 54-99190) have been proposed.

Regarding multilayer structure polymers, for example, Japanese Patent Publication No. 55-27
No. 576 shows that blends of trilayer or multilayer polymers and rigid thermoplastic polymers improve impact resistance without sacrificing transparency.

It is explained that the desirable particle size in this case is 1600A to 2800A. In addition, polymers with a complex structure of five or more layers having an intermediate layer with a monotonous concentration gradient between each of the three layers (hard, soft, and rocky) (Japanese Patent Application Laid-Open No. 51-12944 and Japanese Patent Application Laid-Open No. 5-board bulletin), or soft, stool, soft,
A hard polymer having a four-layer structure (Japanese Unexamined Patent Publication No. 1983-917) has been proposed as an impact modifier with excellent stress whitening resistance. As a result of extensive research into improving the solvent resistance of acrylic resins, the present inventors discovered a method for improving the solvent resistance of acrylic resins without impairing their transparency, weather resistance, and processability, and completed the present invention. I ended up doing it. That is, in the present invention, when the whole is 100 parts by weight, (1) methyl acrylate alone or 2% by weight or less of at least one alkyl acrylate whose alkyl group has 1 to 8 carbon atoms; 20 to 8 parts by weight of a rigid thermoplastic acrylic resin obtained by polymerizing a monomer copolymerizable with these, or a monomer mixture consisting of both of them, and 2 to 8 parts by weight of a leg multilayer structure polymer. 2 parts by weight of a monofunctional monomer copolymerizable with methyl methacrylate alone or 2 parts by weight or less of a monofunctional monomer copolymerizable therewith; The first layer is a hard non-crosslinked polymer with a Tg of 25% or more obtained by emulsion polymerization of a mixture of (0) 45 to 99.9% by weight.
At least 1 alkyl group having 1 to 8 carbon atoms
Copolymerizable with alkyl acrylate and 0.1 to 1% low cloud content of a polyfunctional grafting agent, or with up to 5% by weight of a polyfunctional grafting agent, or up to 4% by weight of these. A first layer formed by polymerizing a monomer, or both, in the presence of the first layer, with a monomer polymer having a Tg of 25°C or lower when polymerized in the absence of the first layer. 2 layers (m) methyl methacrylate alone or with 20
Consisting of at least one alkyl acrylate whose alkyl group has 1 to 8 carbon atoms, or 20% by weight or less of a monomer copolymerizable with these, or both, and the absence of a second layer. Tg when polymerized below is 25℃
A third layer formed by polymerizing the above monomer mixture in the presence of a second layer, and the obtained 3
The layered polymer has a first layer of 5 to 3% by weight and a second layer of 4% by weight.
0-85% by weight, third layer 10-3% by weight (total 10
% by weight) and having a particle size of 200 to 900A.

An object of the present invention is to provide an acrylic resin that has excellent solvent resistance and fluidity without impairing the characteristics of acrylic resin, such as transparency, weather resistance, and processability.

The rigid thermoplastic acrylic resin used in the present invention is composed of methyl methacrylate alone, or together with at least one alkyl acrylate whose alkyl group has 1 to 8 carbon atoms, up to 2% by weight, or up to 20% by weight of these. It can be obtained by polymerizing a monomer polymer consisting of copolymerizable monomers or, if necessary, both of them, by a known method.

The three-layer structure polymer used in the present invention is obtained by emulsion polymerization according to a known method.

In this case, it is necessary that no new particles be generated during polymerization of the second and third layers, and for this purpose a so-called seed polymerization method is employed. That is, when polymerizing the second and third layers, it is necessary not to add an additional emulsifier, or if it is necessary to add it, it is necessary to keep it within a range where new particles are not generated. The first layer of the three-layer structure polymer is obtained by emulsion polymerization of methyl methacrylate alone or a mixture of methyl methacrylate and a copolymerizable monofunctional monomer of 2% or less, and has a Tg of 25°C or higher. It is preferably a hard acrylic resin with a temperature of 50° C. or higher, and it is necessary to have a non-crosslinked structure.

That is, it must not contain any polyfunctional monomers, such as polyfunctional crosslinking agents such as divinylbenzene, polyfunctional grafting agents such as allyl methacrylate, etc. The resulting polymer is therefore soluble in the solvent. By using such a polymer, the final composition has excellent fluidity. It is particularly preferable that the average molecular weight of the first layer polymer is between 50,000 and 200,000. The polymer of the second layer is 45-99. % by weight of at least one alkyl acrylate whose alkyl group has 1 to 8 carbon atoms and 0.1 to 1% by weight of a polyfunctional grafting agent, or together with not more than 5% by weight of a polyfunctional grafting agent; A monomeric crosslinking agent or a monomer copolymerizable with these in an amount of 4% by weight or less, or optionally both. When it is polymerized in a state where it is not heated, it is an acrylic elastomer with a Tg of 0 or less, preferably 0°C or less, and the lower the Tg, the better the solvent resistance at low temperatures of the resulting resin composition. There is.

Alkyl acrylate polymers generally have a lower refractive index than methyl methacrylate polymers, so if a transparent composition is desired, the alkyl acrylate may be copolymerized with a monomer that provides the polymer with a higher refractive index. Transparency is improved by matching the refractive index of the elastic body to that of the hard acrylic resin.

Also, a polyfunctional grafting agent is used to create a chemical bond between the second and third layers.

Without this, the resulting composition may undergo whitening when subjected to stress, exposure to ultraviolet light, or exposure to hot water. By using a polyfunctional grafting agent, the second
Although the elastic body of the layer has a crosslinked structure to some extent, it is possible to further crosslink it by using a polyfunctional crosslinking agent if necessary. The third layer polymer can be copolymerized with methyl methacrylate alone, or with at least one alkyl acrylate whose alkyl group has 1 to 8 carbon atoms in an amount of 2% by weight or more, or with methyl methacrylate in an amount not more than 2% by weight. A monomer polymer consisting of a monofunctional monomer or, if necessary, both.
When polymerized in the absence of a layer, the polymer has a Tg of 25° C. or higher, preferably 5000 or higher.

This third layer polymer is graft-bonded with the second layer to improve the compatibility between the elastic body and the blended resin, and by coating the elastic body, it eliminates the stickiness of the particles and improves handling properties. have an effect. The weight ratio of each layer in the three-layer structure polymer is 5 to 3% by weight for the first layer and 4% by weight for the second layer.
m~85% by weight, and the third layer is 10~3% by weight.

If the first layer is less than 5% by weight, seed polymerization may not be completed completely, and if it is more than 3% by weight, a sufficient effect of improving solvent resistance may not be obtained. If the third layer is less than 1% by weight, the resulting three-layer polymer becomes sticky and has poor handling properties, as well as poor compatibility with the blend resin and poor dispersion. Further, if the amount is more than 3%, the effect of improving solvent resistance cannot be sufficiently obtained. When a three-layer structure polymer is produced by emulsion polymerization, the particle size can be controlled by the amount of emulsifier, and in order to obtain the desired effect in the present invention, it is necessary to strictly control the particle size.

The particle size of the three-layer structure polymer used in the present invention is 200 to 900.
A range of A is required. When the particle size is smaller than 200A, the fluidity of the obtained resin is significantly reduced, and when it is larger than 900A, the solvent resistance and stress whitening resistance are reduced. Grain fleas can be measured in the state of the emulsion at the end of emulsion polymerization by known methods such as electron microscopy, absorbance method, and light scattering method.

In addition, in the case of a composition blended with an acrylic resin, it can be measured using an electron microscope. The three-layer structure polymer of the present invention has superior productivity compared to conventionally proposed polymers.

In the case of emulsion polymerization, it is widely known that as the amount of emulsifier increases, the resulting polymer particles become smaller and the polymerization rate increases. The three-layer structure polymer of the present invention has a particle size of 200~
The polymerization rate is 900A, which is 4.0 mm smaller than other proposals, and the productivity is particularly excellent because the structure is simple with three layers. The alkyl acrylates whose alkyl group has 1 to 8 carbon atoms used in the present invention include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, inbutyl acrylate, 2-ethylhexyl acrylate, etc. These can be used alone or as a mixture of two or more.

Particularly preferred among these are n-butyl acrylate and 2-ethylhexyl acrylate. In addition, copolymerizable monofunctional monomers include aromatic unsaturated monomers represented by styrene, unsaturated nitrile monomers represented by acrylonitrile, and vinyl monomers such as higher acrylates and higher methacrylates. can be mentioned. In particular, as a monomer for adjusting the refractive index, styrene, phenyl methacrylate, naphthyl methacrylate, etc. are preferable. Examples of the polyfunctional grafting agent used in the second layer include allyl esters such as acrylic acid, methacrylic acid, maleic acid, and fumaric acid, with allyl acrylate and allyl methacrylate being particularly preferred.

Examples of the polyfunctional crosslinking agent include acrylic polyalkylene glycol, methacrylic diester, and divinylbenzene. As the polymerization initiator used in the polymerization of the three-layer structure polymer of the present invention, radical polymerization initiators used in ordinary emulsion polymerization can be used, and redox-based polymerization initiators are particularly preferred.

Other chain transfer agents, ultraviolet absorbers, etc. commonly used in polymerization,
Additives can also be optionally used. As the emulsifier, anionic surfactants are particularly preferred, but other emulsifiers commonly used in emulsion polymerization can also be used. The thermoplastic acrylic resin to be blended is produced by commonly used methods such as emulsion polymerization, suspension polymerization, bulk polymerization, and solution polymerization.

The acrylic resin composition of the present invention contains 20 to 3 parts by weight of a hard thermoplastic acrylic resin when the total weight is 10 parts by weight.
It can be obtained by blending 2 to 8 parts by weight of layered polymers.

If the three-layer structure polymer is less than 2 parts by weight, solvent resistance,
Stress whitening resistance is extremely reduced.

The resin composition of the present invention thus obtained has transparency,
Improved solvent resistance without compromising weather resistance or processability.
This is a solvent-resistant acrylic resin composition with good fluidity and productivity.

Next, the present invention will be explained in more detail with reference to Examples.

The particle size in the Examples was measured using an electron microscope. Solvent resistance was determined by supporting an injection-molded dumbbell at one end across a fulcrum, applying a load to the other end, dropping a solvent onto the fulcrum, and measuring the time it took for the test piece to break. Impact resistance is ASTM-D2
It was measured by the V-notched Izod strength according to No. 56.
For whitening, the test piece was pulled and the state of whitening at a predetermined elongation rate was visually examined. The fluidity (melt flow index, hereinafter abbreviated as MI) was determined by the method of ASTM-○12.
The molecular weight of the polymer was measured at 30°C and a load of 3.8k9 using an Ostwald viscometer.

Calculated from the intrinsic viscosity of 390 of the loform solution. Example 1 In a 10mm beaker equipped with a stirrer and a condenser, 5.7mm of distilled water and 21mm of dioctyl sodium sulfosuccinate were added as an emulsifier. Female, Rongalit 1 as reducing agent. Add crab and dissolve evenly.

220 g of methyl methacrylate, 7. n-butyl acrylate as the first layer. Female, n-octyl mercaptan 0.
7g, diisopropylbenzene hydroperoxide 0
．． 23 g of a homogeneous solution was added and polymerized at 8 pi. The reaction was completed in about 18 minutes. The average molecular weight of this polymer was about 80,000. Then, as a second layer, n-butyl acrylate 1
30 females, 300 g of styrene, 1 coat of diethylene glycol diacrylate, 17 g of allyl methacrylate, 1 coat of diisopropylbenzene hydroperoxide. A homogeneous solution of the gunwale was added dropwise over a period of 1 hour.

The reaction was completed approximately 40 minutes after the completion of the dropwise addition. Then, as a third layer, a homogeneous solution of 640 g of methyl methacrylate, 40 g of n-butyl acrylate, 2.0 g of n-octylmercabutane, and 0.7 g of diisopropylbenzene hydroperoxide was added.

The reaction was completed in about 30 minutes. The reaction temperature was then raised to 95°C and held for 1 hour. The particle size of the obtained polymer was approximately 850
It was A. The obtained emulsion was poured into a 0.5% aluminum chloride aqueous solution to coagulate the polymer, washed five times with warm water, and dried to obtain a three-layer structure polymer. On the other hand, acrylic resin beads with an average molecular weight of 100,000 containing 9% by weight of methyl methacrylate and 3% by weight of n-butyl acrylate were prepared by a conventional suspension polymerization method, and a blend resin was prepared using the above-mentioned 3
It was blended with a layered polymer at a predetermined ratio to form a pellet.

Using this, various test pieces were molded and subjected to measurements. The results are shown in Table 1. Table 1 Example 2 Completely the same as Example 1 except that the amount of emulsifier was changed and the particle size was changed.
Various test pieces were molded in the same manner as above and subjected to measurement.

The results are shown in Tables 2 and 3. Comparative Example 1 Completely the same as Example 1 except that the amount of emulsifier was changed and the particle size was changed.
Various test pieces were molded in the same manner as above and subjected to measurement.

The results are shown in Tables 2 and 3. Table 1 2 Three-layer structure polymer (parts by weight) blend resin Table-3 Amount of three-layer polymer (parts by weight) blend resin

Claims (1)

[Claims] 1 When the whole is 100 parts by weight, (A) methyl methacrylate alone, or together with it, 20% by weight or less of at least one alkyl acrylate whose alkyl group has 1 to 8 carbon atoms, or 20% by weight or less Rigid thermoplastic acrylic resins 20 to 9 formed by polymerizing monomers copolymerizable with these, or a monomer mixture consisting of both.
8 parts by weight of (I) methyl methacrylate alone or 2 to 80 parts by weight of (B) a multilayer structure polymer, wherein the multilayer structure polymer contains (I) methyl methacrylate alone or 20 to 80 parts by weight of , the first layer is a hard non-crosslinked polymer with a Tg of 25% or more, which is obtained by emulsion polymerization of a mixture of this and a copolymerizable monofunctional monomer, (II) 45-99.9
% by weight of at least one alkyl acrylate whose alkyl group has 1 to 8 carbon atoms and 0.1 to 10% by weight of a polyfunctional grafting agent, or 5% by weight thereof;
Consisting of the following polyfunctional crosslinking agents, 40% by weight or less of monomers copolymerizable with these, or both,
The second layer (III) is formed by polymerizing a monomer mixture whose Tg is 25°C or lower when polymerized in the absence of the first layer (III) methyl methacrylate alone, or 20% by weight of methyl methacrylate alone. % or less of at least one alkyl acrylate whose alkyl group has 1 to 8 carbon atoms or 20% by weight
It consists of monomers copolymerizable with the following, or both, and has a Tg of 2 when polymerized in the absence of a second layer.
The obtained three-layer structure polymer has a third layer formed by polymerizing a monomer mixture having a temperature of 5° C. or higher in the presence of the second layer, and the obtained three-layer structure polymer has a structure in which the first layer is 5 to 30% by weight, the second layer is 40 to 85% by weight, the third layer is 10 to 30% by weight (total 100% by weight), and the particle size is 200 to 900 Å.
An acrylic resin composition characterized by having the following properties.