JPH08301913A - Production of acrylonitrile/styrene copolymer - Google Patents

Abstract

PURPOSE: To produce an acrylonitrile/styrene copolymer improved in hue by copolymerizing an acrylonitrile monomer with a styrene monomer in the presence of a specified polymerization initiator. CONSTITUTION: An acrylonitrile monomer is copolymerized with a styrene monomer in the presence of a polymerization initiator comprising at least one nonaromatic t-amylperoxy ester represented by the formula (wherein R is 1-20C prim. or sec. alkyl). When an acrylonitrile/styrene copolymer (AS resin) is produced by using a polymerization initiator comprising an aromatic organic peroxide, it is susceptible to discoloration due to the residual aromatic rings of the decomposition product and deteriorates in hue due to the strong hydrogen withdrawing power of the formed phenyl free radicals and benzyl free radicals. When the monomers are copolymerized in the presence of the polymerization initiator of the formula, the product has no aromatic rings and free radicals having a strong hydrogen withdrawing power are not generated; therefore an AS resin improved in hue can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an acrylonitrile-styrene copolymer having an improved color tone.

[0002]

2. Description of the Related Art Conventionally, an acrylonitrile-styrene copolymer (also referred to as AS resin) obtained by copolymerizing an acrylonitrile monomer and a styrene monomer has been used for automobile industrial products, industrial electric equipment parts, It is used in the field of household electric appliance parts and daily sundries, and is also used as a raw material for an acrylonitrile-butadiene-styrene copolymer (also referred to as ABS resin). A container that allows the AS resin to come into direct contact with chemicals, food or cosmetics,
When it is used for equipment, packaging, etc., it is desired that the degree of coloring of the molded product be as low as possible.

The AS resin, like other resins, can be obtained by copolymerizing each monomer in the presence of a polymerization initiator. When an organic peroxide having an aromatic ring is used as a polymerization initiator, the aromatic ring itself of the decomposition product remains, so that the copolymer is easily colored. Further, the phenyl radical and the benzyl radical generated during the polymerization reaction have a strong hydrogen abstraction force, which further deteriorates the hue of the polymer.

On the other hand, as a method of reducing the residual volatile content without lowering the hue, an organic peroxide type polymerization initiator containing no aromatic ring has been studied. For example, in JP-A-53-82892, t-butylperoxy-
A method of using 3,5,5-trimethylhexanoate and t-butylperoxyacetate in combination is disclosed in JP-B-57-2.
Japanese Patent No. 8483 discloses a method in which an azo compound, an organic peroxide containing no aromatic ring, and t-butylperoxyketals are used in combination.

[0005]

However, in the method disclosed in Japanese Patent Laid-Open No. 53-82892, the methyl radical of the decomposition product of t-butylperoxyacetate is hydrogen abstraction like the above-mentioned phenyl radical and benzyl radical. Because of its strong strength, it tends to be colored and a copolymer having a good hue cannot be obtained. The method disclosed in Japanese Examined Patent Publication No. 57-28483 generates a t-butoxy radical because the peroxyketals have a t-butyl group. This radical easily decomposes into acetone and methyl radicals,
Due to the above-mentioned reasons, it is likely to be colored and the hue is similarly insufficient.

Therefore, it is an object of the present invention to provide a method for producing an acrylonitrile-styrene copolymer having an improved color tone.

[0007]

[Means for Solving the Problems] The inventors of the present invention have conducted extensive studies to solve the above-mentioned problems. As a result, when the acrylonitrile monomer and the styrene-based monomer are copolymerized, T containing no aromatic ring represented by the structural formula
It has been found that the use of amyl peroxyesters makes it possible to obtain an intended acrylonitrile-styrene copolymer having an improved color tone, and completed the present invention.

[0008]

Embedded image

(In the formula, R represents a C _1-20 primary or secondary alkyl group.) Further, the organic peroxide of t-amyl peroxyesters and other aromatic rings are not contained. It has been found that an excellent synergistic effect can be obtained by using the organic peroxide in combination, and further by using the organic peroxide and the antioxidant in combination. That is, the present invention uses an acrylonitrile monomer and a styrenic monomer as a polymerization initiator, and uses one or more t-amyl peroxyesters containing no aromatic ring represented by the above formula. Acrylonitrile having improved color tone characterized by copolymerization
The present invention relates to a method for producing a styrene-based copolymer.

The aromatic ring-free t-amyl peroxyesters used in the present invention include t-amyl peroxy acetate, t-amyl peroxyisobutyrate, t-amyl peroxy n-butyrate, t-amylperoxy-2-ethylhexanoate, t-amylperoxy n-octanoate, t-amylperoxy n-pentanoate, t-amylperoxy-2-methylpentanoate, t-amylperoxy n -Hexanoate, t-amyl peroxyisononanoate, t
-Amyl peroxy n-laurate, t-amyl peroxy n-decanoate, t-amyl peroxy-2-ethylbutyrate, t-amyl peroxy n-propionate and t-amyl peroxy n-nonanoate. However, it is not limited thereto.

Further, as the organic peroxide (2) which can improve the color tone when used in combination with the organic peroxide (1) of the present invention, t-octylperoxy-2-
Ethyl hexanoate, t-octyl peroxy n-octate, t-butyl peroxy n-laurate, t
-Butyl peroxy n-octoate, t-hexyl peroxy-2-ethylhexanoate, t-hexyl peroxy-2-ethyl pentanoate, t-hexyl peroxy n-octoate, t-hexyl peroxy acetate and Peroxy esters such as t-hexyl peroxy n-laurate, t-butyl peroxy isopropyl carbonate, t-amyl peroxy isopropyl carbonate, t-hexyl peroxy isopropyl carbonate and peroxy such as t-octyl peroxy isopropyl carbonate Diacyl peroxides such as carbonates, diacetyl peroxide, dipelargonyl peroxide, dilauroyl peroxide, dioctanoyl peroxide and didecanoyl peroxide Although the like, but is not limited to these.

These organic peroxides (1) and (2) are plasticizers such as dioctyl phthalate, IP-solvents,
It may be used by diluting with an organic solvent such as an aliphatic hydrocarbon which is usually commercially available, such as Isozole or Shelsol (both are trade names).

In order to obtain the copolymer of the present invention, tris (2,4-di-t-butylphenyl) phosphite is used as an antioxidant for trapping generated radicals, particularly as a phosphorus-based antioxidant. , Tris (2,4-di-t-butyl-5-methylphenyl) phosphite, tetrakis (2,4-di-t-butylphenyl) -4,4'-biphenylenediphosphonite, bis (2,4) -Di-t-butylphenyl) pentaerythritol diphosphite, bis (2,6-di-t-butyl-4-methylphenyl) pentaerythritol diphosphite, 2,2'-methylenebis (4,6-di- t-butylphenyl) -2-ethylhexyl phosphite, tetrakis (2,4-di-t
Examples include, but are not limited to, -butyl-5-methylphenyl) -4,4'-biphenylenediphosphonite.

Blending ratio of organic peroxides (1) and (2),
The amount used varies depending on the reaction conditions, but in general (1) /
The weight ratio of (2) is preferably 10/0 to 2/8, and (2)
If the ratio is higher than this, the effect of improving the hue tends to be weakened.

The amount of the organic peroxide (1) of the present invention used alone or in the combined use of (1) and (2) is 0.005 to 0. 5% by weight
Is appropriate.

The amount of the antioxidant used is appropriately 0.005 to 0.1% by weight based on the monomer mixture.

A suitable polymerization temperature is 90 ° C. or higher and 170 ° C. or lower. If it is lower than 90 ° C, the polymerization rate is slow and it is not economical, and if it exceeds 170 ° C, the polymerization rate is too fast and it is difficult to control it.

The acrylonitrile monomer used in the present invention may be any one suitable for commercial polymerization. Examples of the styrene-based monomer include styrene, α-methylstyrene, t-butylstyrene, etc., but are not limited thereto.

In the method of the present invention, t-dodecyl mercaptan, n-dodecyl mercaptan, unsaturated dimer of α-methylstyrene, terpinolene, octyl thioglycolate and the like may be used as the molecular weight modifier.

The copolymerization method of the present invention may be a suspension polymerization method, a bulk polymerization method or the like. When the suspension polymerization method is used, the dispersant usually used is, for example, a third dispersant. A sparingly soluble inorganic salt such as calcium phosphate or magnesium phosphate, a water-soluble polymer such as polyvinyl alcohol, methyl cellulose, or the like can be used.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

[0022]

【Example】

Examples 1 to 7 and Comparative Examples 1 to 7 To a mixed monomer liquid of 16.7 g of styrene and 33.3 g of acrylonitrile, a polymerization initiator or an antioxidant of the kind and amount shown in Table 1 was added, 5 ml of the dissolved and adjusted sample was collected in a glass ampoule tube having an inner diameter of 16 mm. Then, after replacing the air in the ampoule with nitrogen gas, the upper part of the ampoule was sealed with a gas burner.

This was immersed in an oil bath, the temperature of the oil bath was raised to the polymerization temperature shown in Table 1 and kept for 5 hours to carry out polymerization.

The hue of the polymer was evaluated according to the following criteria. A: Almost colorless B: Light yellow C: Yellow D: Dark yellow

The abbreviations for the polymerization initiators in the table mean the following, respectively. TBPO: t-butylperoxy-2-ethylhexanoate TAPO: t-amylperoxy n-octoate TAPL: t-amylperoxy n-laurate TAIN: t-amylperoxy isonanoate TBIC: t-butylperto Oxyisopropyl carbonate TAIC: t-amylperoxy isopropyl carbonate TBEC: t-butylperoxy-2-ethylhexanoate TAPB: t-amylperoxybenzoate TBPB: t-butylperoxybenzoate # 70: t-butylperoxy acetate

The abbreviations for the antioxidants in the table mean the following. P-101: tetrakis (2,4-di-t-butyl-5)
-Methylphenyl) -4,4'-biphenylenediphosphonite-based phosphonite antioxidant

[0028]

[Table 1]

[0029]

[Effect of the Invention] When the acrylonitrile monomer and the styrene-based monomer are copolymerized, a specific t
-By using amyl peroxy ester, an acrylonitrile-styrene copolymer having an excellent color tone can be obtained. A copolymer having an improved color tone can be prepared by using another polymerization initiator containing no aromatic ring, and further using an antioxidant such as a phosphorus antioxidant.

Claims (7)

[Claims] 1. An acrylonitrile monomer and a styrene-based monomer are used as a polymerization initiator, and one or more t-amyl peroxyesters having no aromatic ring represented by the following structural formula are used. A method for producing an acrylonitrile-styrene type copolymer having an improved color tone, characterized in that it is copolymerized. Embedded image (In the formula, R represents a C _1-20 primary or secondary alkyl group.) 2. An acrylonitrile monomer and a styrenic monomer are used as a polymerization initiator and do not contain one or more t-amyl peroxyesters according to claim 1 and other aromatic rings. A method for producing an acrylonitrile-styrene copolymer having an improved color tone, which comprises using one or more organic peroxides in combination and copolymerizing them. 3. An organic peroxide containing no acrylonitrile monomer and styrenic monomer, one or more t-amyl peroxyesters according to claim 1 and other aromatic rings. Of one or more of polymerization initiators selected from the group consisting of one or more of the above, and an acrylonitrile-styrene copolymer with improved color tone, characterized by being used in combination with an antioxidant. Manufacturing method. 4. The composition of the monomer mixture is 10 to 95% by weight of styrenic monomer and 90 to 5 of acrylonitrile monomer.
The manufacturing method according to any one of claims 1 to 3, wherein the manufacturing method is% by weight. 5. The total amount of the polymerization initiator used is 0.005 to 0.5% by weight based on the monomer mixture of the acrylonitrile monomer and the styrene monomer. The production method described in Crab. 6. The antioxidant is a phosphorus-based antioxidant,
The amount used is 0.005-0.1% by weight with respect to the monomer mixture of the acrylonitrile monomer and the styrene monomer.
The method according to claim 3, wherein 7. The production method according to claim 1, wherein the polymerization temperature is 90 ° C. or higher and 170 ° C. or lower.