JPH0819199B2 - Method for producing thermoplastic resin - Google Patents

Description

The present invention relates to a method for producing a thermoplastic resin having excellent transparency, weather resistance and impact resistance. More specifically, in the presence of a rubber-like polymer obtained by hydrogenating a block copolymer composed of an aromatic vinyl compound and a conjugated diene compound, (meth) acrylic acid ester and other vinyl monomers copolymerizable therewith are obtained. It relates to a method for producing a thermoplastic resin, characterized in that the composition of the monomer consisting of is selected as a polymer having a refractive index substantially equal to that of the rubber-like polymer, and graft polymerization is carried out.

b. Conventional technology In general, polymethylmethacrylate resin or a resin containing methylmethacrylate as a main component has excellent properties such as transparency, luster, and weather resistance.
It is used in a wide range of fields such as displays, but has the disadvantage of low impact strength. As a method for improving the impact strength, a vinyl-based monomer mixture composed of methyl methacrylate, styrene, acrylonitrile, etc. in the presence of a diene-based rubber such as polybutadiene, a refractive index of the diene-based rubber and a vinyl-based monomer mixture are used. There is known a method in which the composition of a vinyl-based monomer mixture is selected and polymerized so that the refractive index of the polymer obtained by polymerizing the above is substantially the same. For example, a methyl methacrylate-butadiene-styrene copolymer resin and a methyl methacrylate-butadiene-styrene-acrylonitrile copolymer resin obtained by the method are used in various fields. However, since these resins contain unsaturated double bonds in the molecular main chain, they are deteriorated by ultraviolet rays and oxygen in the air, and there is a fatal defect that they are so-called poor weather resistance such as discoloration and deterioration of impact resistance. .

As a method of improving the weather resistance, a method has been proposed in which, instead of the diene rubber, a rubber-like polymer whose molecular main chain is substantially saturated is used, and various vinyl monomers are graft-polymerized thereto. There is. However, since this rubber-like polymer does not have a double bond like diene rubber and has a low radical activity, the vinyl monomer is not graft-polymerized and the rubber-like polymer and the vinyl-polymer resin are simply combined. Often a blend. For this reason, when the obtained resin is injection-molded, the surface has irregularities, gloss and transparency are extremely low, and various properties such as impact resistance and tensile strength are poor.

c. Problems to be Solved by the Present Invention The inventors of the present invention have intensively studied these problems, and as a result, the existence of a rubbery polymer obtained by hydrogenating a block copolymer composed of an aromatic vinyl compound and a conjugated diene compound. It was found below that a thermoplastic resin sufficiently conforming to the above purpose can be obtained by graft-polymerizing a vinyl-based monomer containing (meth) acrylic acid ester as a main component and satisfying specific conditions. Has reached the present invention.

d. Means for Solving the Problems That is, the present invention provides a method for producing a homopolymer in the presence of a rubbery polymer (a) obtained by hydrogenating a block copolymer comprising an aromatic vinyl compound and a conjugated diene compound. A rubber-like polymer (a) is obtained by graft-copolymerizing a monomer (b) consisting of a (meth) acrylic acid ester having a glass transition temperature of 50 ° C. or higher and another vinyl monomer copolymerizable therewith.
Is 5 to 35% by weight based on the total amount of the rubber-like polymer (a) and the monomer (b), and the refractive index of the rubber-like polymer (a) and the monomer (b) Provided is a method for producing a thermoplastic resin for molding a molded article, characterized in that the composition of the monomer (b) is selected so that the difference from the refractive index of the polymer obtained by polymerizing only To do.

 Hereinafter, the present invention will be described in detail.

As a hydrogenated product of a block copolymer composed of an aromatic vinyl compound and a conjugated diene used in the present invention, for example, hydrogenated to a block copolymer represented by a block copolymer of styrene and butadiene, An aliphatic double bond based on a conjugated diene compound is saturated and converted to an olefin polymer.

Examples of the aromatic vinyl compound include styrene, α-methylstyrene and vinyltoluene, and among them, styrene is preferable. Further, as the conjugated diene, butadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-
Butadiene, isoprene and combinations thereof are preferred.

The ratio of aromatic vinyl and conjugated diene is not particularly specified, but in order to maintain impact resistance when used as a resin, aromatic vinyl / conjugated diene is 5-60 / 95-40% by weight. It is preferably 10 to 50/90 to 50, particularly preferably.

The molecular structure of this block copolymer may be linear, branched, radial or a combination thereof,
The block structure may be diblock, triblock, multiblock, or a combination thereof. The steam addition rate of these block copolymers must be 50% or more, preferably 65% or more, and particularly preferably 80% or more. If it is less than 50%, the weather resistance tends to decrease, which is not preferable.

As a method for producing these hydrogenated block copolymers, a general method can be used. Typical methods include, for example, the methods described in Japanese Patent Publication Nos. 42-8704 and 43-6636. As such a hydrogenated block copolymer, commercially available polymer such as KRATON-G (trade name of Shell Chemical Co.) can be used.

In the present invention, as the vinyl monomer graft-polymerized to the hydrogenated block copolymer rubber, it is necessary to use a (meth) acrylic acid ester and another monomer copolymerizable therewith.

As the (meth) acrylic acid alkyl ester,
When it is made into a polymer by itself, it has a glass transition temperature (measured by a differential scanning calorimeter (DSC)) of 50 ° C. or higher, and preferably has 1 to 10 carbon atoms as an alkyl, and more preferably Is 1-6, particularly preferably 1-4. Among methacrylic acid esters and acrylic acid esters, methacrylic acid esters are preferred. Examples of these are methyl methacrylate, ethyl methacrylate, cyclohexyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, t-butylcyclohexyl methacrylate, butyl methacrylate, hexyl methacrylate, represented by the following formula (meth ) Acrylic ester (N is 0 to 3, R is hydrogen or an alkyl group, and m is 3 to
4) and the like, and one or more of these can be used.
Of these, methyl methacrylate and ethyl methacrylate are preferable, and methyl methacrylate is more preferable.

Examples of other copolymerizable vinyl monomers include aromatic vinyl monomers such as styrene, α-methylstyrene and vinyltoluene; vinyl cyanide monomers such as acrylonitrile and methacrylonitrile; acrylic acid. Used in the above (meth) acrylic acid alkyl ester such as methyl, ethyl acrylate, propyl acrylate, butyl acrylate, hexyl acrylate, propyl methacrylate, butyl methacrylate, hexyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate. Other than (meth) acrylic acid alkyl ester monomers; unsaturated acid anhydrides such as maleic anhydride and itaconic anhydride; unsaturated acids such as acrylic acid and methacrylic acid; N-phenylmaleimide, N-cyclohexylmaleimide, etc. Α, β unsaturated dicarboxylic acid Imide compounds.

When the (meth) acrylic acid ester and the above-mentioned copolymerizable monomer are used, the difference between the refractive index of the rubber-like polymer (a) and the refractive index of the monomer mixture (b) is 0.01 or less,
Graft polymerization is carried out by appropriately selecting the composition of the monomer mixture so that it is preferably 0.005 or less. Here, if the difference between the two refractive indexes exceeds 0.01, the transparency of the thermoplastic resin is reduced. The refractive index of the matrix resin composed only of the monomer mixture (b) can be known by calculating from a theoretical formula or by measuring the refractive index of the resin obtained by polymerizing the monomer mixture composed of the composition in advance. it can.

The ratio of the (meth) acrylic acid ester to the other vinyl monomer used is not particularly limited and can be appropriately determined according to the refractive index of the rubber-like polymer (a), but is preferably 30 to
98 / 70-2% by weight, more preferably 50-95 / 50-
5% by weight, particularly preferably 60-90 / 40-10% by weight
Is.

The content of the rubber-like polymer (a) at the time of producing the thermoplastic resin of the present invention can be arbitrarily selected according to the purpose, but it satisfies the impact resistance, moldability and transparency of the resin. The range is 5 to 35% by weight, preferably 10 to 30% by weight
Is. If the rubber content is less than 5% by weight, only a resin having insufficient impact resistance can be obtained, and if it exceeds 35% by weight, surface hardness and moldability are deteriorated, which is not preferable. Therefore,
The monomer mixture (b), which becomes the matrix resin, has the remaining content.

As the polymerization method for producing the thermoplastic resin of the present invention, known methods such as a solution polymerization method, a suspension polymerization method, a bulk polymerization method and an emulsion polymerization method can be adopted. Legal is preferred.

The thermoplastic resin of the present invention thus obtained is transparent,
It has excellent weather resistance and impact resistance, and can be widely used in various applications utilizing these characteristics.

Further, this thermoplastic resin may be blended with other polymers such as a methacrylic acid ester polymer, a styrene-methyl methacrylate copolymer, a styrene-methyl methacrylate-acrylonitrile copolymer depending on the purpose. However, other polymers to be blended, the difference in refractive index between the thermoplastic resin obtained in the present invention and 0.01 or less, preferably in the range of 0.005 or less, preferably in the range, if it does not satisfy this condition, a transparent composition I can't get things.

Incidentally, for the thermoplastic resin of the present invention and the composition using the same, hindered phenol-based, phosphorus-based, and sulfur-based antioxidants, light stabilizers, ultraviolet absorbers, lubricants, colorants, difficult Additives that are commonly used, such as a flame retardant and a reinforcing agent, can be added within a range not impairing the transparency.

e. Examples Hereinafter, the present invention will be described in more detail with reference to Examples. All "parts" and "%" in the examples are based on weight.

The various physical property test methods were measured according to the following points.

(1) Refractive index: Measured at 25 ° C. with an Abbe refractometer.

(2) Izod impact strength: ASTM D-256 (cross section 1/4 x 1/2 inch, with notch) (3) Total light transmittance, haze value: ASTM D-1003 (3.2mm thickness) (4) Weather resistance : Izod impact strength is measured by exposing to a sunshine weatherometer with carbon arc as a light source for 1000 hours. The black panel temperature was 63 ± 3 ° C., and the water showering was 18 minutes every 2 hours.

Example 1 10 parts of hydrogen-containing block copolymer KRATON G-1650 (SEBS manufactured by Shell Chemical Co.) having a refractive index of 1.507, which was previously made into a uniform solution, was placed in a stainless steel autoclave having an internal volume of 10 l equipped with a paddle type stirrer, and styrene. 10.8 parts, toluene 100
Parts, 0.1 part of t-dodecyl mercaptan, were charged and the temperature was raised with stirring, and 79.2 parts of methyl methacrylate, t were added at 50 ° C.
-Butyl peroxyisopropyl carbonate 0.5 part was added. After the system was replaced with nitrogen, the temperature was further raised to 90 ° C., and the polymerization was continued under stirring at this temperature until the polymerization conversion rate became 74%. When the polymerization conversion rate reached 74%, the polymerization was stopped, an antioxidant was added, and then the product was taken out from the autoclave and the unreacted monomer and the solvent were removed by steam distillation. This product was finely pulverized and dried, and then pelletized by an extruder with a 40 mmφ vent. The rubber content of the obtained graft copolymer was 13%, and the refractive index of the copolymer resin composed of only the monomer mixture was 1.5068.

The graft copolymer pellet obtained by the above method was molded into a test piece with an injection molding machine, and the physical properties were measured. The results are shown in Table-1
It was shown to.

Example-2 Hydrogenated block copolymer KRATONG-17 having a refractive index of 1.5105
01X (SEP manufactured by Shell Chemical Co.) 15 parts, styrene 12.8
Parts and 72.2 parts of methyl methacrylate, and a polymerization reaction was carried out in the same manner as in Example-1. After the polymerization was stopped when the conversion of polymerization reached 70%, post-treatment was carried out in the same manner as in Example-1 to obtain a graft copolymer. The rubber content of the obtained graft copolymer was 20%, and the refractive index of the copolymer resin containing only the monomer mixture was 1.5113.

The results of measuring the physical properties of this graft copolymer by injection molding are shown in Table 1.

Example-3 Polymerization, post-treatment and evaluation were carried out in the same manner except that the monomer composition in Example-2 was changed to 12 parts of styrene, 68 parts of methyl methacrylate and 5 parts of acrylonitrile.

The results are shown in Table-1.

The refractive index of the copolymer resin consisting of the monomer mixture was 1.5122.

Example 4 Polymerization was carried out under the following conditions using a polymerization reactor equipped with a paddle type stirrer and connected with two stainless steel autoclaves having an internal volume of 30 liters.

The supply to the reactor was performed from the lower part of the reactor, and two units were connected in a form overflowing from the upper part. After the polymerization solution overflowing from the second reactor was once held in the tank,
It was directly introduced into an extruder with a 65 mmφ vent, the volatile components were separated and removed, and pelletized.

The rubber content of the obtained graft copolymer is 24.8 parts, the refractive index of the copolymer resin consisting of the monomer mixture is 1.
It was 5066.

The results of measuring the physical properties of this graft copolymer by injection molding are shown in Table 1.

Comparative Example-1 <Structure of rubber-like polymer> 0.2 parts of potassium stearate, 1.5 parts of potassium laurate, 0.1 part of sodium alkylnaphthalenesulfonate, potassium hydroxide were placed in a stainless steel autoclave having an inner volume of 100 l equipped with a paddle type stirrer. 0.1 part, potassium chloride 1.
90 parts of ion-exchanged water containing 5 parts was charged, and then 70 parts of n-butyl acrylate and 30 parts of styrene were added. Under a nitrogen atmosphere, the temperature was raised under stirring at 90 rpm and when 45 ° C was reached, potassium persulfate was added, and then the polymerization reaction was performed while controlling to keep it constant at 45 ° C, and the polymerization rate reached 90%. At this point, 0.1 part of diethylhydroxylamine was added to stop the reaction, and unreacted monomers were substantially removed by steam distillation to obtain a rubber-like polymer latex.

This polymer latex was precipitated with Accor, purified, and dried to obtain a rubber-like polymer.

<Production of Graft Copolymer> In place of the hydrogenated block copolymer, the n-butyl acrylate-styrene copolymer elastic body having a refractive index of 1.507 obtained by the above method was used. Polymerization, post-treatment, and evaluation were carried out in the same manner as in Example 1 except for this. The results are shown in Table-1.

Comparative Example-2 <Production of rubber-like polymer> A rubber was prepared in the same manner as in Comparative Example-1, except that the monomer composition in Comparative Example-1 was 50 parts of n-butyl acrylate, 30 parts of 1,3-butadiene and 20 parts of styrene. A polymer was obtained.

<Production of Graft Copolymer> In place of the hydrogenated block copolymer, n-butyl-1,3-butadiene-acrylate having a refractive index of 1.512 obtained by the above method
A styrene copolymer elastic body was used.

Polymerization, post-treatment and evaluation were carried out in the same manner as in Example-2 except for this. The results are shown in Table-1.

Comparative Example-3 Polymerization, post-treatment and evaluation were carried out by the same method except that the monomer composition in Example-1 was 22.5 parts of styrene and 67.5 parts of methyl methacrylate. The results are shown in Table-1.

The refractive index of the copolymer resin composed of only the monomer mixture was 1.5196.

Comparative Example-4 Polymerization, post-treatment and evaluation were carried out in the same manner except that the monomer composition in Example-2 was 34 parts of styrene and 51 parts of methyl methacrylate. The results are shown in Table-1.

The refractive index of the copolymer resin consisting only of monomer mixture is
It was 1.534.

Comparative Example-5 Polymerization, post-treatment and evaluation were carried out by the same method except that the monomer composition in Example-1 was 54 parts of styrene and 36 parts of acrylonitrile. The results are shown in Table-1.

The refractive index of the copolymer resin composed of only the monomer mixture was 1.5628.

Comparative Example-6 Polymerization and post-treatment were carried out in the same manner as in Example-1 except that the base rubber was changed to ethylene-propylene copolymer rubber JSR EPO1P having a refractive index of 1.4855 JSR EPO1P 10 parts, methyl methacrylate 81 parts and methyl acrylate 9 parts. And evaluated. The results are shown in Table-1.

The refractive index of the copolymer resin consisting only of the monomer mixture is
It was 1.4887.

In view of the results shown in Table-1, Examples-1 to 4 have SE
It can be seen that a thermoplastic resin having excellent transparency, weather resistance and impact resistance can be obtained by using a hydrogenated block copolymer such as BS or SEP.

In Comparative Example-1, it can be seen that the impact resistance is remarkably low when the rubber-like polymer having a saturated molecular main chain is used.

In Comparative Example-2, it can be seen that the impact resistance is exhibited by introducing a double bond into the molecular main chain of the rubber-like polymer, but the weather resistance is deteriorated.

Further, according to Comparative Examples 3 and 4, when the difference between the refractive index of the rubber-like polymer and the refractive index of the copolymer resin composed only of the monomer mixture to be graft-copolymerized exceeds 0.01, the transparency is deteriorated. I understand.

f. Effects of the invention As is apparent from the above, according to the present invention, in the presence of a rubbery polymer obtained by hydrogenating a block copolymer comprising an aromatic vinyl compound and a conjugated diene compound, methyl methacrylate and A monomer mixture composed of other copolymerizable vinyl monomers, a composition selected so as to be a polymer having a refractive index substantially equal to that of the rubber-like polymer, and graft-polymerized to obtain transparency, A thermoplastic resin having excellent impact resistance and weather resistance can be obtained.

The thermoplastic resin obtained in the present invention can be formed into various transparent molded products, and can be colored in black or various colors to form molded products having deep and vivid colors. The thermoplastic resin is useful for various home appliances, automobile parts, household products and various other industrial materials, as well as optical materials such as lenses and optical disks.

Claims (2)

[Claims] 1. A glass transition temperature of a homopolymer in the presence of a rubber-like polymer (a) obtained by hydrogenating a block copolymer comprising an aromatic vinyl compound and a conjugated diene compound is 50 ° C. or higher. Graft copolymerization of a monomer (b) consisting of a (meth) acrylic acid ester and another vinyl monomer copolymerizable therewith, and the amount of the rubber-like polymer (a) used is a rubber-like polymer ( 5 for the total of a) and monomer (b)
To 35% by weight, and a single amount so that the difference between the refractive index of the rubber-like polymer (a) and the refractive index of the polymer obtained by polymerizing only the monomer (b) is 0.01 or less. A method for producing a thermoplastic resin for molding a molded article, which comprises selecting the composition of the body (b). 2. The method for producing a thermoplastic resin according to claim 1, wherein the amount of the (meth) acrylic acid ester used in the component (b) is 30 to 98% by weight.