JPH0436184B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an impact modifier that can impart high impact resistance and good moldability. Thermoplastic resins, particularly vinyl chloride resins (hereinafter abbreviated as PVC), are widely used as general-purpose resins, but their mechanical properties are not always satisfactory. That is, PVC has poor impact strength, particularly notched impact strength, and various methods have been proposed to improve this impact strength. The most effective method among these proposals is to mix PVC with a graft copolymer obtained by graft polymerizing a monomer such as styrene, methyl methacrylate, or acrylonitrile onto a conjugated diene elastomer.
Such graft copolymers are already commercially available as impact modifiers for PVC, and are greatly contributing to the expansion of applications for PVC molded products. By the way, in profile extrusion applications, there is a demand for compositions that have very strong slipperiness and have high impact strength even when molded under conditions where kneading is not effective. Modifiers do not provide sufficient results. In other words, multilayer graft copolymers, which are conventional impact modifiers in which a resin component with good compatibility with PVC is graft-polymerized onto an elastomer, do not work well when processed at high temperatures or when a relatively small amount of lubricant is used. While multilayer graft copolymers are uniformly dispersed in PVC and exhibit good impact resistance, multilayer graft copolymers are
It causes agglomeration in PVC and shows almost no impact resistance improvement effect. The present inventors have developed such a multilayer graft copolymer.
As a result of intensive studies based on the idea that uniform dispersion in PVC is the most effective way to improve impact resistance, we found that the glass transition temperature (hereinafter abbreviated as Tg) of the outermost layer is higher than that of conventionally known multilayer graft copolymers. ) is 0°C or less.
When blended with PVC and molded, the dispersion state is good even under high kneading molding conditions, and even under low kneading and low shear stress, the multilayer graft copolymer quickly melts and gels. The company discovered that it was effective as an impact modifier for thermoplastic resins, as it was effective as an impact modifier for thermoplastic resins, as it had a very good dispersion state and could exhibit high impact strength under a wide range of molding conditions. As a result of this study, we found that a specific amount of a specific copolymer containing a specific unsaturated acid monomer as an essential component was added to this multilayer graft copolymer and acted as a more excellent impact resistance modifier. Furthermore, the inventors have discovered that molded products with good processability and excellent surface gloss can be obtained, and have thus arrived at the present invention. That is, the gist of the present invention is that the crosslinking agent is
At least two graft layers are grafted onto a butadiene-based elastomer (A) consisting of polybutadiene or a copolymer containing 50% by weight or more of butadiene and 50% by weight or less of another vinyl compound that can be copolymerized with it. A polymerized multilayer graft copolymer, and the graft layer is made of monomers selected from the monomer group consisting of acrylic acid alkyl esters, methacrylic acid alkyl esters, aromatic vinyl compounds, vinyl cyan compounds, and butadiene. each graft layer contains 0 to 5% by weight of a crosslinking agent with respect to each layer, the glass transition temperature of the polymer constituting the outermost layer (C) is 0°C or less, and the second graft layer from the outermost layer (C) To 100 parts by weight of the multilayer graft copolymer (1) in which the glass transition temperature of the polymer constituting layer (B) is 60°C or higher, 3 to 30 parts by weight of an unsaturated acid monomer is added.
Weight % and vinyl monomers copolymerizable with it 97
Copolymer (2) obtained by copolymerizing ~70% by weight
An impact modifier containing 0.1 to 20 parts by weight. The impact modifier of the present invention is composed of a blend of the multilayer graft copolymer (1) and the copolymer (2), and the multilayer graft copolymer as described above is prepared in at least three stages. It is essential to have a multilayer structure of three or more layers obtained by polymerization, and of course there is no problem even if the graft layer has three or four layers, and the Tg of the polymer constituting the outermost layer is 0. ℃ or less, and the Tg of the polymer constituting the second layer counting from the outermost layer is 60℃ or more. The effect of improving impact resistance is similarly exhibited even when the polymer mixture is polymerized in multiple stages depending on the purpose. The monomer group constituting the multilayer graft copolymer (1), which is a component of the impact modifier of the present invention, is an acrylic acid alkyl ester, a methacrylic acid alkyl ester, an aromatic vinyl compound, a vinyl cyanide compound, and a butadiene. It consists of: The acrylic acid alkyl ester preferably has an alkyl group having 2 to 10 carbon atoms, such as ethyl acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, hexyl acrylate, octyl acrylate, and acrylic acid. Examples include 2-ethyl-hexyl acid. The methacrylic acid alkyl ester preferably has an alkyl group having 1 to 4 carbon atoms, such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, and methacrylic acid. Examples include tertiary butyl. Considering compatibility with PVC, methyl methacrylate is particularly preferred. In addition, aromatic vinyl compounds include styrene,
Examples include α-substituted styrene, nuclear-substituted styrene, and derivatives thereof, such as α-methylstyrene, chlorostyrene, vinyltoluene, and the like. Furthermore, examples of vinyl cyanide compounds include acrylonitrile and methacrylonitrile. Furthermore, examples of butadiene include 1,2-butadiene and 1,3-butadiene. The outermost layer (C) component constituting the multilayer graft copolymer (1) is selected from the above monomer group so that the outermost layer (C) itself has a Tg of 0° C. or less. The composition ratio of the monomers in the outermost layer (C) is 0 to 100% by weight of alkyl acrylate, 0 to 40% by weight of alkyl methacrylate, 0 to 40% by weight of aromatic vinyl compound, and 0% by weight of vinyl cyanide compound. ~
It can be used in a range of 40% by weight and butadiene in a range of 0 to 100% by weight. If the Tg of the outermost layer (C) itself exceeds 0°C, it is difficult to obtain the desired impact resistance improvement effect sufficiently. Furthermore, acrylic acid alkyl ester is preferable to butadiene in that it can be polymerized under normal pressure. The proportion of the outermost layer (C) in the total amount of the multilayer graft copolymer is preferably 10 to 60% by weight, and 10% by weight.
If the ratio is less than
If the proportion exceeds 60% by weight, the molding processability when blended with PVC and molded becomes poor, which is not preferable. Also, the second layer (B) counting from the outermost layer (C)
The components are selected from the above monomer group so that the Tg of the layer (B) itself is 60°C or higher. Layer (B)
The composition ratio of the monomers in the range is 0 to 100% by weight of alkyl methacrylate, 0 to 100% by weight of aromatic vinyl compound, 0 to 100% by weight of vinyl cyanide, and 0 to 20% by weight of alkyl acrylate. Available in Tg of layer (B) itself is 60
If the temperature is below 0.degree. C., the multilayer graft polymer particles tend to aggregate, resulting in poor impact resistance. The components of layer (B) are:
When blended with PVC, methacrylic acid alkyl esters are preferred, particularly methyl methacrylate. Aromatic vinyl compounds improve the fluidity of PVC during blend molding, but when used in large amounts, compatibility deteriorates and impact resistance decreases. Vinyl cyanide compounds are preferable because they promote gelation when blended with PVC, but if used in large amounts, they tend to become discolored during molding, and their processability deteriorates. The proportion of the layer (B) in the total amount of the multilayer graft copolymer is preferably 20 to 60% by weight, and a proportion of less than 20% by weight is not preferable because molding processability when blended with PVC and molded is poor. Also 60% by weight
If the ratio exceeds the above, the amount of the elastomer component in the entire multilayer graft copolymer decreases, which is not preferable because the effect of improving impact resistance is small. The butadiene-based elastomer (A) contains a rubber component that becomes the base of the multilayer graft copolymer, and this rubber component contains polybutadiene or 50% by weight or more of butadiene and 50% by weight of another vinyl compound that can be copolymerized with it.
It is a copolymer of: Other vinyl compounds that can be copolymerized include styrene, acrylonitrile, alkyl acrylates, alkyl methacrylates, and the like. The proportion of the butadiene-based elastomer (A) in the total amount of the multilayer graft copolymer is preferably 10 to 60% by weight, and if the proportion is less than 10% by weight, the effect of improving impact resistance is small. In addition, if the proportion exceeds 60% by weight, not only will it be difficult to coagulate the emulsion polymer latex, but
It is not preferred because it has poor moldability when blended with PVC and molded. The crosslinking agent in the present invention not only facilitates graft crosslinking during the production of the multilayer graft copolymer, but also greatly improves the coagulation properties of the emulsion polymer latex. As a crosslinking agent, divinylbenzene, diacrylic ester or dimethacrylic ester which is an ester of acrylic acid or methacrylic acid and polyhydric alcohol, or triallyl cyanurate, triallyl isocyanurate, allyl acrylate, allyl methacrylate, itacon. Examples include diallyl acid and diallyl phthalate. Note that in consideration of graft cross-reactivity, a crosslinking agent having an allyl group is preferable. The proportion of the crosslinking agent in each layer is 0 to 5% by weight. If it is used in an amount exceeding 5% by weight, the elastic properties of the butadiene elastic layer (A) or layer C will deteriorate too much. In addition, the resin layer (B) is not preferable because its compatibility with PVC deteriorates, and the effect of improving impact resistance in both cases decreases. The proportion of the crosslinking agent in each layer is within the range of 0.1 to 3% by weight, considering the coagulation properties of the emulsion polymer latex during production of the multilayer graft copolymer and the effect of improving the impact resistance of the obtained multilayer graft copolymer. is preferred. The multilayer graft copolymer of the present invention is usually preferably produced by emulsion polymerization of a monomer selected from the above monomer group or a mixture thereof in the presence of a butadiene-based elastomer (A) latex. Examples of emulsifiers include anionic surfactants such as fatty acid salts, alkyl sulfate ester salts, alkylbenzene sulfonates, alkyl phosphate ester salts, and dialkyl sulfosuccinates, as well as polyoxyethylene alkyl ethers and polyoxyethylene fatty acid esters. , sorbitan fatty acid ester,
Nonionic surfactants such as glycerin fatty acid esters and cationic surfactants such as alkylamine salts can be used. These surfactants can be used alone or in combination. As a polymerization initiator, an inorganic initiator such as a normal persulfate, an organic peroxide, an azo compound, etc. may be used alone, or the above compound and a sulfite, hydrogen sulfite, thiosulfate, primary It can also be used as a redox initiator in combination with metal salts, sodium formaldehyde sulfoxylate, etc. Preferred persulfates as initiators include sodium persulfate, potassium persulfate, ammonium persulfate, etc., and organic peroxides include t-
These include butyl hydroperoxide, cumene hydroperoxide, benzoyl peroxide, lauroyl peroxide, etc. A chain transfer agent may be used to adjust the molecular weight of the polymer, and alkyl mercaptans having 5 to 20 carbon atoms can be used. Polymerization is carried out at a temperature higher than the decomposition temperature of the initiator under normal emulsion polymerization conditions, at least the outermost layer (C), the second layer (B) from the outermost layer (C), and the butadiene-based elastomer (A) as described above. This can be done to create a structure like this. At this time, the polymerization at each stage can be carried out by adding the entire amount of each monomer or a mixture of monomers at once, or while continuously adding the entire amount or a portion thereof. The monomers or monomer mixtures can also be polymerized in one or more stages. Copolymer (2), which is another component of the impact modifier of the present invention, contains 3 to 30% by weight of unsaturated acid monomer and 97 to 70% by weight of vinyl monomer copolymerizable therewith. It is obtained by copolymerizing the following, and the preferred method for producing it is emulsion polymerization. Examples of unsaturated acid monomers include acid group-containing monomers such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, cinnamic acid, maleic anhydride, and tenticarboxylic acid. If the amount of unsaturated acid monomer in the copolymer (2) is less than 3% by weight, the effect of improving impact resistance will be small even when blended with the multilayer graft copolymer (1) as an impact modifier. Undesirable. Also
If it exceeds 30% by weight, the latex obtained by emulsion polymerization will not be stable, and when blended with the latex of the multilayer graft copolymer (1) described above, the stability of the latex will deteriorate, and it may be blended with PVC. This is not preferable because the processability during processing may deteriorate. Examples of vinyl monomers copolymerizable with unsaturated acid monomers include acrylic acid alkyl esters, methacrylic acid alkyl esters, aromatic vinyl compounds, vinyl cyan compounds, and butadiene.
These monomer groups mentioned above can be used alone or in combination. When producing the copolymer (2) by emulsion polymerization, the same emulsifiers, polymerization initiators, chain transfer agents, etc. that can be used in producing the multilayer graft copolymer (1) are used. It is possible to
Copolymerization can be carried out in the same manner as in the production of multilayer graft copolymer (1). The impact resistance modifier of the present invention is a blend of the multilayer graft copolymer (1) and copolymer (2) obtained as described above, and the blending ratio is 100% by weight of the multilayer graft copolymer (1). parts, copolymer (2)
is 0.1 to 20 parts by weight. If the amount of copolymer (2) is less than 0.1 part by weight, the effect of improving impact resistance will be small, and if the amount exceeds 20 parts by weight, the latex blended with both copolymers will become unstable. Both are undesirable. When carrying out the present invention, the multilayer graft copolymer (1) and the copolymer (2) are blended at the above-mentioned blending ratio in terms of solid content, and this blended latex is usually salted out, Alternatively, it may be coagulated by acid precipitation, washed with water and recovered in powder form, or spray-dried or freeze-dried and recovered in powder form. It can also be recovered by the method described in JP-A-57-187322. Furthermore, a method may be adopted in which the individual powders of the multilayer graft copolymer (1) and the copolymer (2) are blended later. Particularly preferred is the method of obtaining the latex blend described above. The impact modifier of the present invention, when mixed with various thermoplastic resins, imparts high impact resistance and good processability to the thermoplastic resin, and also improves the surface gloss of molded products. It is. The proportion of the impact modifier of the present invention mixed with the thermoplastic resin is 3 to 3 parts by weight per 100 parts by weight of the thermoplastic resin.
50 parts by weight. If the blending ratio is less than 3 parts by weight, the effect of improving impact resistance will be small, and if the blending ratio exceeds 50 parts by weight, the inherent mechanical properties of the thermoplastic resin will be impaired, so both are not preferred. Here, thermoplastic resins include PVC, polycarbonate resin,
Examples include polyester resin, acrylonitrile-styrene resin, methyl methacrylate-styrene resin, and the like. As PVC, in addition to polyvinyl chloride, a vinyl chloride copolymer containing 70% by weight or more of vinyl chloride can be used. As the monomer copolymerized with vinyl chloride, ethylene, propylene, vinyl bromide, vinylidene chloride, vinyl acetate, acrylic ester, methacrylic ester, etc. are used. The impact modifier of the present invention and the thermoplastic resin are preferably blended in powder form using, for example, a ribbon blender, a Henschel mixer, etc., and are blended using a known kneading machine, such as a mixing roll, a Banbury mixer, an extruder, or an injection molding machine. It is molded using a molding machine or the like. In addition, when compounding, known stabilizers, plasticizers, lubricants, colorants, etc. may be added as necessary. The impact resistance modifier of the present invention contains a specific copolymer containing a specific unsaturated acid monomer as an essential component, and therefore has superior impact resistance modifiers compared to conventional impact resistance modifiers. be effective. The present invention will be specifically explained below using Examples.
In the examples, "parts" and "%" mean "parts by weight" and "% by weight," respectively. Furthermore, the Tg of the copolymer was determined using the Fox equation. Example 1 (a) Production of rubber elastic body (A) Rubber elastic body A was synthesized according to the following composition. 1,3-butadiene 100 parts Divinylbenzene 0.3" Diisopropylbenzene hydroperoxide 0.2" Sodium pyrophosphate 0.5" Ferrous sulfate 0.01" Dextrose 1.0" Potassium oleate 0.5" Water 200" A mixture of the above composition was heated in a pressure autoclave for 50"
Polymerization was carried out at ℃. Polymerization was completed in 15 hours.
The average particle size of the obtained rubber was 0.16μ. (b) Production of multilayer graft copolymer (1) To 30 parts of the rubber latex obtained in (a) above (as polymer solid content), add 0.6 parts of semi-cured beef tallow potash soap and 0.2 parts of sodium formaldehyde sulfoxylate to water. A solution of 120 parts was added thereto, and the temperature was raised to 70°C while stirring. The temperature of this latex was maintained at 70°C, and a mixture consisting of 39.8 parts of methyl methacrylate, 0.2 parts of triallyl isocyanurate, and 0.15 parts of cumene hydroperoxide was added dropwise as a layer (B) component over 2 hours and 30 minutes. After the dropwise addition was completed, the mixture was maintained for 1 hour to complete the first stage graft polymerization. The polymerization rate was 99.8%. To the obtained polymer latex, 0.3 parts of semi-hardened beef tallow potash soap and 0.2 parts of sodium formaldehyde sulfoxylate dissolved in 20 parts of water were added, and acrylic acid n-
Butyl 29.8 parts, triallyl isocyanurate
A mixture consisting of 0.2 part of cumene hydroperoxide and 0.15 part of cumene hydroperoxide was added dropwise over 2 hours while maintaining the temperature at 70°C, and after the completion of the dropwise addition, the mixture was maintained for 1 hour to complete the polymerization. The polymerization rate was 99.6%, and the particle size of the final graft copolymer was 0.21μ.
In the obtained multilayer graft copolymer (1), the Tg of the butadiene-based elastomer was -85°C, and the layer (B)
The Tg of layer (C) was 105°C, and the Tg of layer (C) was -54°C. (c) Production and blending of copolymer (2) Pour 200 parts of ion-exchanged water purged with nitrogen into a reaction vessel, dissolve 3 parts of semi-hardened beef tallow fatty acid soap, 0.6 parts of potassium persulfate, 90 parts of ethyl acrylate,
A mixture consisting of 10 parts of methacrylic acid was added dropwise over 4 hours while maintaining the temperature at 70°C, and the mixture was maintained for 3 hours to polymerize to obtain copolymer (2) latex. The polymerization rate was 99.9% or more. (d) Latex blend and polymer recovery Multilayer graft copolymer (1) Latex 100
Part by weight (as solid content) was placed in a reaction vessel equipped with a stirrer, and 2 parts of copolymer (2) latex (as solid content) was added over 10 seconds while stirring.
Stirring was performed for a minute. The obtained latex mixture was added to an aqueous sulfuric acid solution, solidified by acid precipitation, washed, dehydrated, and dried, and the polymer was recovered in powder form (Example 1-1)). Table 1 also shows examples in which the amount of copolymer (2) added was varied. (e) Production of blended composition with vinyl chloride resin 100 parts of vinyl chloride resin with an average degree of polymerization of 1100, 1.0 part of tribasic lead sulfate, and 0.3 part of dibasic stearic acid.
parts, lead stearate 2.4 parts, stearic acid 0.3 parts
1 part, 0.3 parts of polyethylene wax, and 10 parts of each of the modifiers obtained in (d) above were added, and the mixture was heated to 115° C. in a Henschel mixer to obtain a homogeneous mixture. This vinyl chloride composition was formed into a square bar using a 30 mm single screw extruder under the following conditions.

[Table] The impact strength of the molded product was measured in accordance with ASTM D-256, except that a test piece with a 2 mm deep U-notch was used. The results of these measurements are shown in Table 1.

[Table] From the above results, it can be seen that the effect of improving impact resistance is improved by blending copolymer (2). Example 2 In (a) of Example 1, 1,3-butadiene 100
Instead of 100 parts of a mixture of 1,3-butadiene/styrene in the ratio shown in Table 2, component B is a mixture of 27.9 parts of styrene, 0.1 part of allyl methacrylate, 11.9 parts of methyl methacrylate, and 0.1 part of allyl methacrylate. (a) and (b) of Example 1, except that a mixture consisting of parts of ) The polymerization procedure was carried out in the same manner as in ). 100 parts (as a solid content) of the multilayer graft copolymer (1) latex thus obtained and 4 parts (as a solid content) of the copolymer (2) latex obtained in (c) of Example 1 were latex blended. , (d) and (e) of Example 1
Table 2 shows the impact resistance of vinyl chloride compositions obtained in the same manner as above. This resin composition exhibits good transparency because the multilayer graft copolymer has the same refractive index as PVC. In addition, the impact resistance improvement effect of similarly changing the A component, B component, and C component was shown in Examples 2-2), 2-3), and Comparative Examples 3 and 4.
It is also shown in Table 2.

[Table] The abbreviations in Table 2 are as follows. (B) Ingredients are 2
It is polymerized in stages. Bd: 1,3-butadiene St: Styrene MMA: Methyl methacrylate AMA: Allyl methacrylate 2EHA: 2-ethylhexyl acrylate In Table 2, Examples 2-1) and 2-2)
and of the diene elastomer (A) component of Comparative Example 3.
The ratio of Bd and St is Bd/St=75/25 parts, respectively, and the diene elastic body (A) of Example 2-3)
The ratio of the components Bd and St is Bd/St=60/40 parts, and that of Comparative Example 3 is Bd/St=30/70 parts. From the above results, it can be seen that component (A) or component (C) having a high Tg has little impact resistance improvement effect. Example 3 As copolymer (2) latex, a mixture consisting of 85 parts of butyl acrylate and 15 parts of acrylic acid was polymerized in the same manner as in Example 1 (c) to obtain copolymer (2) latex. Ta. 3 parts (as solid content) of this copolymer (2) latex was added to (a) of Example 1,
A vinyl chloride resin obtained by blending the multilayer graft copolymer (1) obtained in (b) with 100 parts of latex (as solid content) and operating in the same manner as in (d) and (e) of Example 1. The impact resistance of the compositions is shown in Table 3. Table 3 also shows the evaluation results of copolymer (2) latexes with different compositions and amounts added.

【table】

[Table] The abbreviations in Table 3 are as follows BA: n-butyl acrylate AA: acrylic acid IA: itaconic acid EA: ethyl acrylate MA: methyl acrylate MAA: methacrylic acid CA: crotonic acid The results show that copolymer (2) latexes with a small amount of unsaturated acid have little effect on improving impact resistance, and those with a large amount of unsaturated acid deteriorate the stability of the latex after blending. Example 4 20 parts of the modifier obtained in (a) to (d) of Example 1, 80 parts of polycarbonate resin, 0.2 part of antioxidant, and 0.1 part of calcium stearate were mixed in a Henschel mixer, and the cylinder temperature was It was pelletized using a 30 mmφ extruder set at 240°C. After drying, a test piece was prepared using an injection molding machine, and the impact strength was measured using the same evaluation method as in Example 1 (e). Table 4 shows the results. Table 4 also shows the results of various changes in the amount of copolymer (2) added.

[Table] As described above, the modifier according to the present invention exhibits a good impact resistance improving effect on polycarbonate resin.

Claims (1)

[Scope of Claims] 1. A butadiene-based elastomer containing 0 to 5% by weight of a crosslinking agent and consisting of polybutadiene or a copolymer of 50% by weight or more of butadiene and 50% by weight or less of another vinyl compound that can be copolymerized with it. A multilayer graft copolymer in which at least two graft layers are graft-polymerized to (A), and the graft layers are composed of an acrylic acid alkyl ester, a methacrylic acid alkyl ester, an aromatic vinyl compound, a vinyl cyanide compound, and butadiene. It is composed of monomers selected from the monomer group, each graft layer contains 0 to 5% by weight of a crosslinking agent, and the glass transition temperature of the polymer constituting the outermost layer (C) is 0. ℃
Hereinafter, 100 parts by weight of a multilayer graft copolymer (1) in which the glass transition temperature of the polymer constituting the second layer (B) from the outermost layer (C) is 60°C or higher is added to 3 to 3 parts by weight of an unsaturated acid monomer. 30% by weight and at least one vinyl monomer selected from acrylic acid alkyl esters, methacrylic acid alkyl esters, aromatic vinyl compounds, vinyl cyanide compounds, and butadiene 97~
Copolymer (2) obtained by copolymerizing 70% by weight
An impact modifier containing 0.1 to 20 parts by weight. 2 A polymer in which the proportion of the butadiene-based elastomer (A) in the multilayer graft copolymer (1) is 10 to 60% by weight, and the outermost layer (C) constitutes the layer (C) from among the monomer group. A polymer consisting of 95 to 100% by weight of at least one monomer selected such that the glass transition temperature of percentage is 10-60
Weight%, the second layer (B) from the outermost layer (C) is
95 to 100% by weight of at least one monomer selected from the monomer group so that the glass transition temperature of the polymer constituting layer (B) is 60°C or higher and 0 crosslinking agent.
The impact resistance modifier according to claim 1, characterized in that the impact resistance modifier is a polymer comprising 20 to 60% by weight of the multilayer graft copolymer.