JP2003128712A - Methacrylic resin and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a methacrylic resin having narrow molecular weight distribution and free from discoloration in melt-molding process. SOLUTION: The methacrylic resin is produced by carrying out the radical copolymerization of a raw material containing an acrylic acid ester and a methacrylic acid ester in the presence of a RAFT (reversible addition- fragmentation chain transfer) agent which is a kind of a chain transfer agent and optionally decoloring the product with an oxidizing agent or a nucleophilic reagent. The invention further provides a method for the production of the resin.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a methacrylic resin by radical polymerization, and more specifically, to a methacrylic resin by radical copolymerization of a methacrylic acid ester and an acrylic acid ester using a RAFT agent and its production. It is about the method.

[0002]

2. Description of the Related Art In recent years, addition cleavage type chain transfer reaction (Rev
erasable Addition-Fragmen
station Chain Transfer: RAF
The method for producing a high molecular compound by the T method) has characteristics that it can be applied to various monomers, that a wide range of reaction conditions can be used, and that a resin having a narrow molecular weight distribution can be obtained. Has been attracting attention. The RAFT method is one of living radical polymerization methods, and is a method of polymerizing a compound capable of reversibly undergoing addition-cleavage-chain transfer reaction as a chain transfer agent (hereinafter referred to as RAFT agent), for example, WO98. / 0147
8, WO99 / 31144 and WO00 / 75207 describe inventions relating to a method for synthesizing a polymer compound using various thiocarbonylthio compounds as RAFT agents. Also, Macromolecules 199
8, 31, 5559-5562 includes a unique thiocarbonylthio compound (RAFT agent) in the above RAFT method.
A treatment method using a peroxide or the like has been introduced for the purpose of reducing the red coloration derived from.

[0003]

However, as the methacrylic resin obtained by the RAFT method, for example, W.
In O98 / 01478 or WO99 / 31144, polymethylmethacrylate is obtained by radical polymerization of methylmethacrylate, but this polymethylmethacrylate is red, and when it is subjected to melt molding, the molded product is colored yellow. It was observed that this yellow coloration could not be decolorized by the treatment with the above-mentioned peroxide.

[0004]

Means for Solving the Problems As a result of intensive studies in view of the present situation, the present inventors have found that the methacrylic monomer has
The methacrylic resin obtained by radical copolymerization with an acrylic monomer in the presence of an AFT agent can be obtained as a white powder by decolorization treatment, and even if this is melt-molded, a molded product without yellow coloring is obtained. I found that The present invention has been made based on such findings. That is, the gist of the present invention is a novel methacrylic resin and a method for producing the same by radically copolymerizing a raw material containing an acrylic ester and a methacrylic ester in the presence of a RAFT agent. The method for producing a methacrylic resin includes the step of decolorizing with a reagent. Hereinafter, the present invention will be described in detail.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The novel methacrylic resin produced by the production method of the present invention can be obtained by radically copolymerizing an acrylic acid ester-based monomer when radically polymerizing a methacrylic acid ester by the RAFT method. As the RAFT agent which is one of the chain transfer agents used in this reaction,
The following thiocarbonylthio compounds described in the above-mentioned International Publication can be used.

For example, benzyl dithiobenzoate, 1-phenylethyl dithiobenzoate, cumyl dithiobenzoate,
1-Acetoxylethyl dithiobenzoate, hexakis (thiobenzoylthiomethyl) benzene, 1,4-bis (thiobenzoylthiomethyl) benzene, 1,2,4,
5-tetrakis (thiobenzoylthiomethyl) benzene, 1,4-bis- (2- (thiobenzoylthio) prop-2-yl) benzene, 1- (4-methoxyphenyl) ethyl dithiobenzoate, benzyl dithioacetate, Ethoxycarbonylmethyl dithioacetate, dithiobenzoic acid 2-
(Ethoxycarbonyl) prop-2-yl, 2-cyanoprop-2-yl dithiobenzoate, t-dithiobenzoate
Butyl, 2,4,4-trimethylpent-2-yl dithiobenzoate, 2- (4-chlorophenyl) prop-2-yl dithiobenzoate, S-benzyldiethoxyphosphinyldithioformate, t-butyltriti Operbenzoate, 2-phenylprop-2-yl 4-chlorodithiobenzoate, 2-phenylprop-2-yl 1-dithionaphthalate, 4-cyanopentanoic acid dithiobenzoate, dibenzyltetrathioterephthalate, dibenzyltrithiocarbonate , Carboxymethyldithiobenzoate, poly (ethylene oxide) with dithiobenzoate end, and the like. Among these, benzyl dithiobenzoate, 1-phenylethyl dithiobenzoate,
Cumyl dithiobenzoate, benzyl dithioacetate and the like are preferable because they can be synthesized at low cost.

The radical copolymerization method can be applied to any polymerization method such as a solution polymerization method, a suspension polymerization method and an emulsion polymerization method. At that time, a known radical polymerization initiator may be added to the raw material, or ultraviolet rays may be irradiated, or heating may be performed to raise the temperature.

The methacrylic acid ester-based monomer constituting the methacrylic resin of the present invention includes an ester of an alcohol having 1 to 18 carbon atoms and methacrylic acid, an ester of cyclohexanol and methacrylic acid, an epoxy group or a hydroxyl group, An ester derivative of alcohol and methacrylic acid having a substituent such as an amino group, an allyl group and a halogen is preferable because it is easily available. Of these, methyl methacrylate is most preferable. The acrylic acid ester-based monomer, which is a copolymerization component, has 1 to 18 carbon atoms.
Of the above-mentioned methacrylic acid, such as ester of alcohol with acrylic acid, ester of cyclohexanol with acrylic acid, or ester derivative of alcohol with acrylic acid having a substituent such as epoxy group, hydroxyl group, amino group, allyl group and halogen. An ester compound with an alcohol of the same type can be mentioned as a preferable compound.

The amount of the acrylic ester monomer used in producing the methacrylic resin is 0.1 to 50 m in the raw material.
It is preferably used in the range of ol%. It is more preferably 0.5 mol% to 30 mol%, and further preferably 1 mol% to 20 mol%. If the amount of the acrylic acid ester-based monomer is too large, the characteristics of the methacrylic resin may be impaired.
On the other hand, if the amount is too small, a methacrylic resin having a good color tone may not be obtained. In addition to the methacrylic acid ester and the acrylic acid ester, other copolymerizable monomers may be copolymerized as long as the characteristics of the methacrylic resin are not impaired. Examples of the copolymerizable monomer include methacrylic acid, acrylic acid, styrene, acrylonitrile, divinylbenzene, maleic anhydride, N-phenylmaleimide and N-cyclohexylmaleimide.

The number average molecular weight of methacrylic resin is RAF
By increasing or decreasing the amount of T agent used, a methacrylic resin having a desired number average molecular weight can be obtained. In addition, the methacrylic resin obtained by the production method of the present invention has a feature that the molecular weight distribution represented by the weight average molecular weight / number average molecular weight is narrower than that of the methacrylic resin obtained by the conventional production method. The methacrylic resin thus obtained does not become yellow during molding, but red coloring due to the RAFT agent (thiocarbonyl structure) is unavoidable. However, this red coloring is due to the above-mentioned Macromo
can be decolorized by treatment with an oxidant such as m-chloroperbenzoic acid or sodium hypochlorite described in Lecles magazine or the like, or a nucleophile such as ammonia, a primary amine or a secondary amine. it can.

[0011]

EXAMPLES Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

Example 1 A reaction vessel equipped with a stirrer and a reflux condenser was charged with 442 parts by mass of deionized water, 4 parts by mass of sodium dodecylbenzenesulfonate, and 0.488 parts by mass of benzyl dithiobenzoate (PhCSSBzl), The atmosphere was degassed with nitrogen, and the temperature was raised to 85 ° C. Subsequently, a radical polymerization initiator V-50 (2,2′-azobis (2-amidinopropane) dihydrochloride: manufactured by Wako Pure Chemical Industries, Ltd.) 0.488 parts by mass and a mixture of deionized water 20 parts by mass were added. ,
A mixture of 98 parts by mass of methyl methacrylate (98.4 mol%) and 2 parts by mass of butyl acrylate (1.6 mol%) was added dropwise over 50 minutes, and then the mixture was heated and stirred for 1 hour, followed by methyl methacrylate / acrylic acid. A latex composed of a butyl copolymer was obtained. Coagulate and recover this methyl methacrylate / butyl acrylate copolymer latex,
Drying gave a red powder. Next, the red powder was dissolved in dichloromethane, 1.5 mol of m-chloroperbenzoic acid was added to 1 mol of the thiocarbonylthio structure, and the mixture was stirred for several minutes for decolorization. By adding the obtained colorless transparent solution to excess methanol,
A white powder composed of a methyl methacrylate / butyl acrylate copolymer was obtained.

Example 2 A red powder consisting of a methyl methacrylate / butyl acrylate copolymer was obtained in the same manner as in Example 1 except that the decolorizing treatment was not carried out.

Example 3: As a RAFT agent, cumyl dithiobenzoate (PhC) was used instead of benzyl dithiobenzoate.
A white powder made of a methyl methacrylate / butyl acrylate copolymer was obtained according to the method described in Example 1 except that 0.544 parts by mass of SSCm) was used.

Example 4 A red powder consisting of a methyl methacrylate / butyl acrylate copolymer was obtained in the same manner as in Example 3, except that the decolorizing treatment was not carried out.

COMPARATIVE EXAMPLE 1 Similar to the method described in Example 1, except that 100 parts by weight of methyl methacrylate was used instead of 98 parts by weight of methyl methacrylate and 2 parts by weight of butyl acrylate. Thus, a white powder made of a polymer of methyl methacrylate alone was obtained.

Comparative Example 2: The same as the method described in Example 2 except that 100 parts by mass of methyl methacrylate was used instead of 98 parts by mass of methyl methacrylate and 2 parts by mass of butyl acrylate. Thus, a red powder composed of a polymer of methyl methacrylate alone was obtained.

Comparative Example 3: The same method as in Example 3 was repeated except that 100 parts by mass of methyl methacrylate was used instead of 98 parts by mass of methyl methacrylate and 2 parts by mass of butyl acrylate. Thus, a white powder made of a polymer of methyl methacrylate alone was obtained.

Comparative Example 4: Similar to the method described in Example 4, except that 100 parts by mass of methyl methacrylate was used instead of using 98 parts by mass of methyl methacrylate and 2 parts by mass of butyl acrylate. Thus, a red powder composed of a polymer of methyl methacrylate alone was obtained.

Comparative Example 5: N-octyl mercaptan (OctSH) 0.28 as a chain transfer agent (non-RAFT agent) was used in place of benzyl dithiobenzoate RAFT agent.
Same as Example 2 except that 8 parts by mass was used,
A white powder composed of a methyl methacrylate / butyl acrylate copolymer was obtained.

Comparative Example 6 A white powder made of a methyl methacrylate / butyl acrylate copolymer was obtained in the same manner as in Example 2 except that benzyl dithiobenzoate was not used. .

With respect to each of the polymers obtained in Examples 1 to 4 and Comparative Examples 1 to 5, a test piece was prepared by melt injection molding after drying, and the following test and evaluation were performed on the test piece. <Polymerization rate> A part of the latex after polymerization is heated at 170 ° C. to 3
The solid content was measured by heating and drying for 0 minutes to obtain the polymerization rate. <Weight average molecular weight (Mw), number average molecular weight (Mn)> W
A calibration curve was prepared from a PMMA standard sample of known molecular weight using a 510 type GPC manufactured by Aters Inc., and each average molecular weight was determined.

<Color tone> It is carried out by visually observing the appearance,
Those having the same transparency as those polymerized using octyl mercaptan (Comparative Example 5) were evaluated as colorless. The results of the above tests and evaluations are summarized in Table 1.

[0024]

[Table 1]

From the above results, the following has become clear. Molded articles obtained by melt-molding the methacrylic resin (Examples 1 to 4) obtained by copolymerizing the methacrylic acid ester-based monomer of the present invention with the acrylic acid ester-based monomer retain the color tone of the resin before molding. On the other hand, in the molded products of methacrylic resin (Comparative Examples 1 to 4) obtained by homopolymerization of methacrylic acid ester, yellow coloring was observed regardless of the presence or absence of decolorization treatment.

[0026]

EFFECTS OF THE INVENTION As is clear from the above description, the methacrylic resin containing the acrylic acid ester-based monomer as the copolymerization component utilizing the RAFT method (radical copolymerization method) of the present invention is almost colored during melt molding. It is possible to obtain a molded product having the color tone of the resin itself without the color tone.
Therefore, the present invention provides various effects based on the characteristic that the methacrylic resin has a narrow molecular weight distribution and provides a special effect that a molded product having a desired color tone can be provided.

Claims (3)

[Claims] 1. A method for producing a methacrylic resin in which a raw material containing an acrylic acid ester and a methacrylic acid ester is radically copolymerized in the presence of a RAFT agent. 2. The method for producing a methacrylic resin according to claim 1, further comprising a step of decolorizing with an oxidizing agent or a nucleophile after the copolymerization step. 3. A methacrylic resin obtained by the method according to claim 1 or 2.