JPS623853B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a graft polymer for reinforcing impact-resistant vinyl chloride resins that have excellent weather resistance and tensile strength. As is well known, vinyl chloride resins have good mechanical and chemical properties and are widely used commercially. However, the disadvantage of vinyl chloride resins is that they have poor impact resistance, and various methods for improving this are known. For example, a widely used method is to mix butadiene-styrene-methyl methacrylate copolymer, or in some cases a resin made by copolymerizing this with unsaturated nitrile, with vinyl chloride resin to improve impact resistance. ing. However, since these copolymers contain a large amount of double bonds in their main chains, they rapidly deteriorate when left outdoors, resulting in extremely low impact resistance. Therefore, without impairing this impact resistance,
Many reinforcing agents that also have weather resistance have been proposed. Typical examples include ethylene-vinyl acetate copolymer rubber grafted with vinyl chloride, and cross-linked acrylic acid ester-based rubber grafted with methyl methacrylate, styrene, and acrylonitrile monomers. Are known. However, these still have insufficient impact resistance and a significant decrease in tensile strength. On the other hand, a method has also been proposed in which methyl methacrylate is graft-polymerized onto acrylic ester-butadiene copolymer rubber (Japanese Patent Publication No. 40-9628). However, since this method uses methyl methacrylate as the graft component, although it has excellent thermal stability, it has the drawback that it is difficult to develop impact strength. The inventors of the present invention have conducted extensive research to overcome these drawbacks and have discovered an interesting fact. That is, when methyl methacrylate is graft-polymerized to the acrylic ester-butadiene copolymer rubber, the amount of methyl methacrylate used as a graft polymerization component is ethyl acrylate, butyl acrylate, ethyl methacrylate, and butyl methacrylate. , when the polymer is combined with a monomer with a low glass transition temperature (Tg), extremely high impact strength is developed, and furthermore, using these monomer components with a low Tg can improve the impact strength. found that although the tensile strength decreased significantly, this problem could be resolved by a two-stage graft polymerization method, and that this two-stage graft polymerization method exhibited a remarkable effect regardless of the presence or absence of butadiene in the base rubber polymer. It was. That is, depending on the use and purpose for which it is used, butadiene may be introduced into the base rubber polymer within a range that does not impair weather resistance. As a result, the strength is further improved compared to when a crosslinked acrylic acid ester is used as the backbone rubber polymer, and the backbone rubber polymer can be selected depending on the purpose and use. That is, an impact-resistant vinyl chloride resin composition having excellent tensile strength and weather resistance over a very wide range can be obtained.
Furthermore, since the graft polymer of the present invention does not contain unsaturated nitrile as an essential component, it has excellent thermal stability and causes no problems in terms of food hygiene. Based on the above-mentioned findings, we have succeeded in obtaining a graft polymer that provides a weather-resistant and impact-resistant vinyl chloride resin composition with excellent tensile strength that has not been previously available. In the present invention, an acrylic acid alkyl ester having an alkyl group having 2 to 12 carbon atoms, preferably 2 to 5 carbon atoms,
99.95% by weight preferably 59.9-99.9% by weight and butadiene 0-49.55% by weight preferably 0-40% by weight and polyfunctional crosslinker 0.05-5% by weight preferably 0.1-
Stem rubber polymer 50 to 80 copolymerized with 3% by weight
In the presence of parts by weight () methyl methacrylate 50
~90% by weight preferably 60-80% by weight and styrene 10
5 to 45 parts by weight, preferably 10 to 25 parts by weight, of a mixed monomer consisting of ~50% by weight, preferably 20 to 40% by weight, are first graft-polymerized, and then 25 to 90% of methyl methacrylate as an essential component is graft-polymerized. Weight% Preferably 50-80% by weight and 10-75% of one or more monomers selected from ethyl acrylate, butyl acrylate, ethyl methacrylate, and butyl methacrylate.
The weight% is preferably 20 to 50% by weight, and the glass transition temperature Tg of the polymer is 0°C to 90°C.
Preferably, it is a graft polymer obtained by graft polymerizing 5 to 35 parts by weight of mixed monomers at a temperature of 20 to 80°C. This will be explained in detail below. The degree of weather resistance deterioration of a butadiene-containing vinyl chloride resin reinforcing agent is controlled by the butadiene content in the reinforcing agent. In other words, if the butadiene content in the trunk rubber polymer exceeds approximately 50%, the weather resistance enhancement ability of the reinforcing agent will be significantly lost, so the butadiene content in the trunk rubber polymer should be set within a range that does not impair the weather resistance enhancement ability. There is a need. That is, the base rubber polymer used needs to be selected depending on the intended use of the reinforcing agent. When weather resistance is more important, the butadiene content is kept small, or sometimes it is not included at all.On the other hand, when strength is important, it is preferable to copolymerize butadiene with acrylic acid alkyl ester to the extent that weather resistance is not impaired. Yes. This is because when using an acrylic acid alkyl ester-butadiene copolymer rubber, as the butadiene content increases, the glass transition temperature of the copolymer rubber decreases, which is advantageous for developing strength. The base rubber polymer of the present invention is usually produced by emulsion polymerization. The acrylic acid alkyl ester used at this time has an alkyl group having 2 to 12 carbon atoms, and may be linear or branched. Examples include ethyl acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, benzyl acrylate, hexyl acrylate,
Examples include n-octyl acrylate and 2-ethylhexyl acrylate. These monomers can be used alone or in combination. It is essential to copolymerize the acrylic acid alkyl ester and butadiene monomer with a polyfunctional crosslinking agent in order to improve impact resistance. The polyfunctional crosslinking agent is used in an amount of 0.05 to 5% by weight in the rubber monomer, preferably
It is necessary in a range of 0.1 to 3% by weight, and if this range is exceeded, the effect of imparting impact resistance is significantly reduced. Examples of polyfunctional crosslinking agents include ethylene glycol diacrylate, diethylene glycol diacrylate,
Polyhydric alcohols such as triethylene glycol diacrylate, tetraethylene glycol diacrylate, 1,3-butylene glycol diacrylate, 1,4-butylene glycol diacrylate, 1,6-hexene glycol diacrylate, trimethylolpropane triacrylate, etc. Di- or triacrylates, di- or trimethacrylates of polyhydric alcohols corresponding to the above acrylic acids, divinyl ethers of polyhydric alcohols such as ethylene glycol divinyl ether, polyvinyl esters of polybasic acids such as divinylbenzene, divinyl adipate, etc. , polybasic acids such as diallyl phthalate, diallyl maleate, diallyl fumarate, diallyl sebecate, di- or triallyl esters, triallyl compounds such as diallyl ether, triallyl cyanurate, triallyl isocyanurate, triallylphosphate, etc. Examples include polyfunctional unsaturated compounds such as allyl esters of polymerizable carboxylic acids such as allyl methacrylate, allyl acrylate, allyl itaconate, monoallyl fumarate, and monoallyl maleate. Among these polyfunctional crosslinking agents, crosslinking agents containing di- or triacrylates of polyhydric alcohols and allyl groups are particularly preferred. The backbone rubber polymer should be 50 to 80 parts by weight in the graft polymer. If the amount is less than 50 parts by weight, the effect of improving the impact resistance of the resulting composition of the graft copolymer and vinyl chloride resin will be small. or,
If it exceeds 80 parts by weight, it will become lumpy during the salt (acid) precipitation or drying stage, making it difficult to mix uniformly with the vinyl chloride resin, which will cause variations in the physical properties of the resulting molded product. The aqueous dispersion of the trunk rubber polymer is preferably obtained by an emulsion polymerization method, and a known method is used as the emulsion polymerization method, in which the rubber monomer is mixed with an emulsifier,
The entire amount may be initially charged together with the initiator and other additives, or the entire amount or a portion thereof may be added continuously or intermittently while polymerization proceeds. The average primary particle diameter of the base rubber polymer latex can be 0.08 to 0.3μ, but the average particle diameter of 0.12 to 0.4, which is obtained by adding a flocculant to this rubber latex to cause micro-agglomeration, can be used.
It is also possible to use μ agglomerated rubber particles. As the flocculant, hydrochloric acid, sulfuric acid, inorganic salts, organic acids and organic acid anhydrides, which are generally used as latex flocculants, and organic substances having flocculating properties can be used. The graft polymerization in the present invention is usually carried out in two stages with 20 to 50 parts by weight of the graft monomer in an aqueous medium containing emulsified and dispersed 50 to 80 parts by weight of the above-mentioned trunk rubber polymer. It is essential that the first stage is composed of a mixed monomer of methyl methacrylate and styrene. That is, the first stage component is
By mainly comprising methyl methacrylate and styrene, it maintains the high tensile strength of the vinyl chloride resin and provides excellent impact resistance and strength. Specifically, in the first stage composition, if the amount of methacrylic acid methyl ester is less than 50% by weight, the tensile strength decreases rapidly and it is difficult to develop impact resistance strength, whereas if it is 90% by weight or more, it is difficult to develop impact resistance strength. . Furthermore, if the styrene content is less than 10% by weight, the strength development ability is poor, while if it is more than 50% by weight, the tensile strength is significantly reduced. The second-stage graft monomer composition has the role of obtaining higher strength, which is difficult to obtain with a graft polymer obtained by graft-polymerizing only the first-stage monomer. The type and amount of ethyl acrylate, butyl acrylate, ethyl methacrylate, and butyl methacrylate to be copolymerized with methyl methacrylate in the second-stage graft monomer must be carefully considered. That is, if the glass transition temperature of the second-stage graft component is too low, the tensile strength will drop significantly, and in extreme cases, it will become lumpy during coagulation and drying, making uniform mixing with the vinyl chloride resin difficult. On the other hand, if the glass transition temperature is too high, it becomes difficult to develop impact resistance. In other words, in order to maintain the high tensile strength of vinyl chloride resin while stably providing high strength development ability, the Tg of the second-stage graft component should be adjusted from 90℃ to 0.
It is essential to keep the temperature above ℃. The Tg of the second-stage graft component does not necessarily need to be measured, and is expressed as the sum of the weight fraction of each monomer in the second-stage graft component multiplied by the Tg of the homopolymer of each monomer. It is practical to substitute numerical values. In addition, in the present invention, a polymer handbook (Polymer handbook) is used.
The values in Table 1 below in the Handbook) were used as the Tg of the homopolymer of each monomer.

[Table] Monomers to be graft-polymerized are graft-polymerized in the second stage after substantially completing the polymerization in the first stage.
The monomers at each stage can be polymerized in whole or in part by adding them continuously or all at once. Graft polymerization may be carried out using known redox-type initiator systems or thermally decomposed initiators. The graft polymer obtained by the above method may be salted out, coagulated, and dried by known methods, and at this time it is also possible to co-coagulate it with an aqueous dispersion of vinyl chloride resin or the like. It is also possible to add known antioxidants, ultraviolet absorbers, heat stabilizers such as vinyl chloride resins, etc. during coagulation. The graft polymer obtained by the above method is mixed with a vinyl chloride resin to form a vinyl chloride resin composition that has weather resistance, impact resistance, and excellent tensile strength. Mixed in a way. In the case of powder mixing, a Henschel mixer, a Banbury mixer, a ribbon blender, etc. are used. The amount of the graft polymer composition mixed with the vinyl chloride resin varies depending on the application, but generally 3% of the graft polymer is mixed with 97 to 70% by weight of the vinyl chloride resin.
~30% by weight. In addition, as vinyl chloride resin, vinyl chloride homopolymer or vinyl chloride is 70% by weight.
Examples include copolymers containing the above. In addition, specific processing aids, stabilizers, ultraviolet absorbers,
It is also possible to add lubricants, fillers, antistatic agents or, if necessary, plasticizers. Examples will be shown below, where parts are by weight. Example 1 The following components were charged into a pressure vessel and polymerized at 40°C for 12 hours. Water 150 parts n-Butyl acrylate 45 Butadiene 15 Ethylene glycol dimethacrylate 1.0 Ferrous sulfate (FeSO _{4.7H 2} O) 0.005 Ethylenediamine tetraacetate disodium salt 0.01 Sodium formaldehyde condensed naphthalene sulfonate 0.2〃 Sodium oleate 3.0 parts Cumene hydroperoxide 0.05〃 Sodium formaldehyde sulfoxylate
0.05〃 The average particle size of the obtained rubber latex is 0.1μ
The polymerization yield was 99%. To the obtained base rubber polymer latex, 0.13 parts of hydrogen chloride and 0.33 parts of 0.33% hydrochloric acid aqueous solution were gradually added to cause agglomeration, and then 2% sodium hydroxide aqueous solution was added to stabilize the mixture. Ta. Rubber latex has an average particle size
It was aggregated to 0.15μ. To this, the graft components shown below were polymerized at 60°C for 4 hours. The polymerization rate was 98%. First-stage graft polymerization component Methyl methacrylate 15 parts Styrene 5 Cumene hydroperoxide 0.1 Sodium formaldehyde sulfoxylate
0.2〃 Ethylenediaminetetraacetic acid disodium salt 0.01〃 Ferrous sulfate 0.005〃 Further, the following second-stage graft polymerization components were added to the obtained latex and polymerized in the same manner at 60°C for 4 hours. The polymerization rate was 98%. Second-stage graft polymerization components Methyl methacrylate 15 parts Ethyl acrylate 5 Cumene hydroperoxide 0.2 The obtained polymer latex was salted out and dehydrated and dried to obtain the intended graft polymer. The obtained graft polymer was molded into a 1-inch hard vinyl chloride pipe of 80 mm diameter under the following lead compounding conditions.
This was carried out using a bidirectional twin-screw salt extractor. Blended polyvinyl chloride (degree of polymerization 1000) 100 parts Graft polymer of the present invention 7 Lead stabilizer 2.0 Calcium stearate 1.0 Wax lubricant 0.5 The physical properties of the molded product were as shown in Table 2. Examples 2 to 6, Comparative Examples 1 to 15 Examples 2 to 6 and Comparative Examples 1 to 15 are summarized in Table-
Shown in 2. All polymerization conditions and mixing molding conditions with vinyl chloride resin other than those listed in Table 2 are the same as in Example 1. Examples 1 to 6 that satisfy the conditions of the present invention are shown in Table-
As shown in No. 2, it has excellent impact resistance and tensile strength. However, those that do not satisfy even one of the conditions of the present invention have low impact strength or a significant decrease in tensile strength. That is, even if two-stage graft polymerization is carried out, as shown in Comparative Example 1, if the Tg of the second-stage graft component is higher than the range of the present invention, although the tensile strength is excellent, it is difficult to develop strength, and as shown in Comparative Example 9, the Tg When Tg is lowered to below 0°C, strength is developed, but the tensile strength is significantly lowered, and when the Tg is further lowered as in Comparative Example 3, it becomes lumpy and it is difficult to form a uniform structure with the vinyl chloride resin. In addition, ethyl acrylate, butyl acrylate, ethyl methacrylate, butyl methacrylate, and the monomers must be copolymerized with methyl methacrylate, and when these monomers are used alone, they are used as comparative examples. As shown in No. 8, no strength was developed and the tensile strength decreased significantly. As shown in Comparative Example 7, when the amount of the first-stage graft component increases beyond the range of the present invention, the degree of decrease in tensile strength decreases, but no strength is developed, and the amount of the second-stage graft component increases beyond the range of Comparative Example 6. As shown in the figure, when the amount exceeds the range of the present invention, the tensile strength decreases significantly. In addition, Comparative Examples 14 and 15 were carried out without performing the two-stage graft polymerization of the present invention.
As shown in Figure 2, in order to develop strength using the one-stage graft polymerization method, large amounts of ethyl acrylate, butyl acrylate, ethyl methacrylate, and butyl methacrylate monomers are required, resulting in a significant decrease in tensile strength. Moreover, in extreme cases, as shown in Comparative Example 15, the mixture becomes lumpy, making it difficult to mix uniformly with the vinyl chloride resin. Furthermore, as shown in Comparative Example 13, when the amount of methyl methacrylate in the first stage graft component is increased beyond the scope of the present invention, strength is not developed, and Comparative Example 10,
As shown in Figures 11 and 12, it can be seen that when the amount of styrene is increased beyond the range of the present invention, the tensile strength decreases significantly.

【table】

[Table] Examples 7, 8, 9 A mixed solution of the monomer components shown in Table 3 and 0.2 part of yumene hydroperoxide was heated for 4 hours while stirring the following components in a nitrogen stream while maintaining the temperature at 40°C. The polymerization was progressed by adding the polymer over a period of time. Water 150 parts Sodium oleate 1.5 Sodium formaldehyde condensed naphthalene sulfonate 0.2 Sodium formaldehyde sulfoxylate
0.4〃 Sodium ethylenediaminetetraacetate 0.01〃 Ferrous sulfate 0.005〃 Sodium phosphate dodecahydrate 0.5〃

[Table] In all cases, the conversion rate was 98% or higher. Example 1 was applied to the obtained trunk rubber polymer latex.
Graft polymerization was carried out in the same manner as above, and after salting out and drying, the mixture was mixed with vinyl chloride resin and molded. Comparative Examples 16 and 17 The polymerization conditions and mixing molding conditions with vinyl chloride resin other than those listed in Table 4 were all the same as in Example 7.

【table】

Claims (1)

[Claims] 1 50 to 99.95% by weight of an acrylic acid alkyl ester having an alkyl group having 2 to 12 carbon atoms and 0 butadiene.
~49.55% by weight and 0.05-5% by weight of polyfunctional crosslinker
In the presence of 50 to 80 parts by weight of a core rubber polymer obtained by copolymerizing First, graft polymerization is carried out, () After that, 25 to 90% by weight of methyl methacrylate and 10 to 75% by weight of one or more monomers selected from ethyl acrylate, butyl acrylate, ethyl methacrylate, and butyl methacrylate. %
and the glass transition temperature of the polymer is set between 0°C and 90°C 5
A graft polymer for reinforcing vinyl chloride resin, which is obtained by graft polymerizing ~35 parts by weight.