JPS6126803B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention is a method for bulk or suspension polymerization of styrenic monomers using a specific organic peroxide as a catalyst, and the polymer has little residual monomer, has a high molecular weight, and has excellent mechanical strength. The purpose is to obtain a styrenic polymer. Various methods have been known for producing high molecular weight polymers by polymerizing styrene monomers. For example, there is a method in which a crosslinking agent is present in the polymerization system. When processed, the polymer produced by this method has poor fluidity and causes flashing and flow mark phenomena, so it cannot be molded into commercial products. Therefore, there are methods to increase the molecular weight to some extent by lowering the polymerization temperature or reducing the amount of catalyst to improve these drawbacks, but these are not preferred because the yield per unit time decreases. In addition, there is a method of producing a styrene-based high molecular weight polymer using a catalyst with a specific structure, but this method does yield a high molecular weight polymer, but the content of residual monomers in the polymer is low, Moreover, it is not possible to obtain a product with excellent mechanical strength (Japanese Patent Publication No. 46-4577,
52-151383). There is also a method using diperoxyketal having a specific structure as a catalyst, and it is recognized that this method can certainly yield styrenic polymers with a low content of styrene monomers. However, the production of low molecular weight styrene monomers is unavoidable, and mechanical strength cannot be said to be excellent. As explained above, there are advantages and disadvantages to the physical properties of styrenic polymers produced by conventional methods.In addition, styrenic polymers have a low residual monomer content, high molecular weight, and excellent mechanical strength. There is no known method for producing styrenic polymers with good processability. As a result of extensive research into a polymerization method for styrenic monomers that satisfies these properties at the same time, the present inventor has discovered that styrene can be produced by combining catalysts selected from the two groups (A) and (B). Based on the knowledge that the object of the present invention can be achieved by polymerizing the monomers,
This completes the present invention. That is, the present invention (A)
Di-tert-butyl peroxyisophthalate, di-tert-butyl peroxy 2,4,
Organic filtration of one or more selected from 4-trimethyl adipate and di-tert-butyl peroxy-2,2,4-trimethyl adipate, and peroxyketals and alkyl peresters with a half-life of 100°C or higher. Among oxides, (B)
Tertiary butyl peracetate, Tertiary butyl peroxybenzoate, Ethyl 3,
3-bis(tertiary-butylperoxy)butyrate, methyl 3,3-bis(tertiary-butylperoxy)butyrate, 2,2-bis(tertiary-butylperoxy)butane and n-butyl 4,4-bis(tertiary-butylperoxy)butane It is characterized in that it is used in combination with one or more selected from the group consisting of (butylperoxy)valerate to form a catalyst. The present invention will be explained in more detail below. The present invention is a method of polymerizing styrenic monomers using a specific catalyst, and produces a well-balanced styrenic polymer with low residual monomer content, high molecular weight, and excellent mechanical strength, especially falling weight strength. However, it is essential to use a combination of organic peroxides selected from groups (A) and (B) as catalysts, and it is essential to use a combination of organic peroxides selected from groups (A) and (B). Groups alone cannot achieve this goal. All of the peroxides in group (A) are difunctional organic peroxides, and each molecule contains two peroxide bonds. Furthermore, due to the steric structure within the molecule, the active sites have polymerization reactivity, which is thought to have different cleavage temperatures, and the polymerization reaction proceeds from the peroxide bond that is cleaved at a certain temperature, resulting in a peroxide bond at the end of the polymer. It is presumed that a reaction occurs in which a polymer containing an oxide bond is formed, and then the other peroxide is cleaved and the polymer radicals bond together to form a high molecular weight. The amount of the catalyst used in the present invention is preferably 0.01 to 0.5% by weight based on the styrenic monomer.
It is 0.05 to 0.25%, and if it is less than 0.01%, there is no substantial effect, and if it exceeds 0.5%, the polymerization rate is high.
It becomes difficult to control the removal of reaction heat, etc. The ratio of organic peroxides used in group (A) and group (B) may be arbitrary, and by varying the ratio and polymerization temperature, the desired styrenic polymer can be sufficiently obtained. The ratio of group ) and group (B) used is preferably 1:2 to 3:1 on a weight basis. The polymerization temperature is preferably 80 to 150°C. If it is lower than 80°C, it is suitable for obtaining a high molecular weight styrenic polymer, but it takes a significant amount of time to obtain a polymer with a small amount of residual monomer. The yield per unit time is low, and
When the temperature exceeds 150°C, the reaction rate increases significantly, making it difficult to smoothly control polymerization. Examples of the styrenic monomer used in the present invention include styrene, α-methylstyrene, vinyltoluene,
Tertiary-butylstyrene may be used alone or as a mixture thereof, and these styrene monomers may be mixed with copolymerizable monomers such as acrylonitrile and methyl methacrylate. Further, in the present invention, during polymerization, a molecular weight regulator such as mercaptans and a plasticizer such as white mineral oil or butyl stearate for improving moldability can also be added. The styrenic polymer obtained in this way has a better balance of intrinsic viscosity, residual monomer content, and mechanical strength than conventional polymers, and has excellent processability, as well as extremely high falling weight strength. It is suitable as an injection molding resin, and is molded and used for durable products such as parts for electrical equipment and machinery, audio products, and medical instruments. Next, the present invention will be further explained with reference to Examples. Example 1 Add 25 kg of pure water and 150 g of tribasic calcium phosphate to an autoclave with a capacity of 60, stir at 180 rpm,
Next, 25 kg of styrene, 20 g of di-tertiary butyl peroxyisophthalate, and 2,2.
Bis(tert-butylperoxy)butane 25
g was added, the inside of the autoclave was purged with nitrogen gas, and then the autoclave was sealed. Next, the temperature was started to increase and polymerization was carried out at 110°C for 5 hours, then the temperature was raised to 120°C and polymerization was carried out for 2 hours, and then the temperature was maintained at 140°C for 3 hours and cooled. The mixture was then neutralized, dehydrated and dried according to conventional methods. Furthermore,
The styrene polymer was made into a regular pellet shape using an extruder. Example 2 As a catalyst, 15 g of di-tert-butyl peroxy 2,4,4-trimethyl adipate, 10 g of di-tert-butyl peroxy 2,2,4-trimethyl adipate, ethyl 3,3-bis(tert-butyl peroxy) ) A styrene polymer was obtained in the same manner as in Example 1, except that 7.5 g of butyrate and 5 g of tert-butyl peracetate were added and polymerized at 95°C for 3 hours, at 110°C for 2 hours and 30 minutes, and at 135°C for 3 hours. . Example 3 90 kg of pure water in an autoclave with a capacity of 200,
Add 500 g of calcium phosphate and 0.4 g of sodium dodecylbenzenesulfonate, continue stirring at 130 rpm, and add 90 kg of styrene, 90 g of di-tert-butyl peroxyisophthalate, 27 g of tert-butyl peroxybenzoate, and n-butyl 4,4-bis(tert-butyl). 36 g of butylperoxy)valerate was added, the inside of the autoclave was purged with nitrogen gas, and then the autoclave was sealed. Next, the temperature was started to increase, and after polymerization was carried out at 105°C for 2 hours, the temperature was raised to 115°C and polymerization was carried out for 3 hours and 30 minutes. The mixture was then maintained at 135°C for 3 hours, cooled, neutralized and dehydrated and dried according to a conventional method. The dried polymer beads were shaped into pellets using an extruder. Example 4 In Example 2, methyl 3,3-bis(tertiary-butylperoxy) was substituted for ethyl 3,3-bis(tertiary-butylperoxy)butyrate.
A styrene polymer was obtained in the same manner as in Example 2 except that 7.5 g of butyrate was used. Comparative Example 1 As a polymerization initiator, 10 g of tert-butyl peroxybenzoate and ethyl 3,3-bis(tert-butyl peroxy) butyrate
A styrene polymer was obtained in the same manner as in Example 1 except that 12.5 g was used. Comparative Example 2 Styrene was used in the same manner as in Example 2, except that di-tert-butyl peroxy 2,4,4-trimethyl adipate and di-tert-butyl peroxy 2,2,4 trimethyl adipate were used as polymerization initiators. A polymer was obtained. Comparative Example 3 57.5 g of penzoyl peroxide as a polymerization initiator other than groups (A) and (B), 8.75 g of tert-butyl peroxybenzoate and ethyl 3,3-bis(tert-butyl) as a polymerization initiator of group (B). A styrene polymer was obtained in the same manner as in Example 1, except that 7.5 g of peroxy)butyrate was used, polymerization was carried out at 90°C for 6 hours, at 115°C for 3 hours, and held at 135°C for 2 hours.

[Table] The physical properties shown in the above table were measured by the following method. (1) Intrinsic viscosity: The specific viscosity of 0.5%, 1.0% and 1.5% toluene solutions was measured, and [η] was determined by a conventional method. (2) Residual styrene monomer: According to Ministry of Health and Welfare Notification No. 98. (3) Bending strength: According to ASTM D-790. (4) Heat distortion temperature: According to JIS K-6871. (5) Falling weight strength: The 3mm part of the injection molded step plate has a weight tip of 5R, weight diameter of 14mmφ, and weight.
Strength is expressed as the height at which a 50g weight is dropped and no cracks occur. Molding was carried out at 230°C using a 2-ounce in-line screw SJ 45A made by Meiki. It should be noted that molded products formed by injection molding are susceptible to directionality, and even when they break due to external force, they tend to break in the direction of the molding flow. Since this point falling weight strength is the easiest to find the direction of, in the present invention, the falling weight strength is adopted as an expression suitable for the actual situation.

Claims (1)

[Scope of Claims] 1. Polymerization of styrenic monomers, characterized in that one or more organic peroxides selected from the following groups (A) and (B) are used as catalysts: Method. (A) Di-tert-butyl peroxy isophthalate, di-tert-butyl peroxy 2,4,4-trimethyl adipate and di-tert-butyl peroxy 2,2,4 trimethyl adipate (B) tert-butyl peracetate , tertiary-butyl peroxybenzoate, ethyl 3,3-bis(tertiary-butylperoxy)butyrate, methyl 3,3-bis(tertiary-butylperoxy)butyrate, 2,2
-bis(tert-butylperoxy)butane and n-butyl 4,4-bis(tert-butylperoxy)valerate.