JPH02218703A - Method for polymerizing vinyl monomer - Google Patents

Abstract

PURPOSE:To prevent a polymer from crosslinking and cleaving in the latter half of polymerization and obtain a vinyl polymer by polymerizing a vinyl monomer in the presence of a specific compound, such as dimethylbutyl isopropyl peroxycarbonate, as a polymerization initiator. CONSTITUTION:A vinyl monomer alone or a mixture thereof with a vinyl monomer copolymerizable therewith is polymerized in the presence of one or more of the group consisting of 1,1-dimethylbutyl isopropyl peroxycarbonate, 1,1- dimethylpropyl isopropyl peroxycarbonate, pinanyl isopropyl peroxycarbonate and 1,1,3,3-tetramethylbutyl isopropyl peroxycarbonate as a polymerization initiator.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention uses a specific polymerization initiator when polymerizing a vinyl monomer alone or a mixture of a vinyl monomer copolymerizable with the vinyl monomer. In particular, the present invention relates to a method for polymerizing vinyl monomers in which the polymerization can be completed near the end point of the polymerization by preventing crosslinking or cleavage of the polymer formed up to that point.

(Prior Art) Conventionally, methods have been known in which various organic peroxides are used as polymerization initiators when polymerizing a vinyl monomer alone or a mixture of a vinyl monomer copolymerizable with the vinyl monomer. The criteria considered when selecting a polymerization catalyst is generally the relationship between the polymerization rate and the molecular weight of the polymer to be formed. The relationship between polymerization rate and molecular weight is usually inversely proportional. When a specific initiator is used, in order to increase the polymerization rate, the amount of initiator used is increased or the polymerization temperature is raised, but as a result, the molecular weight of the resulting polymer decreases.

It is known that the mechanical properties of the resulting polymer are generally better as the molecular weight of the polymer increases.

For this reason, it is important to produce a polymer with a high polymerization rate and high molecular weight. For this purpose, various methods using peroxides as initiators have been developed.

For example, Special Publication No. 36-5391, Special Publication No. 40-2671
3. Japanese Patent Publication No. 47-7891 describes a method in which two or three types of initiators are used in combination. In these published patents, benzoyl peroxide is used as a low temperature initiator, and a peroxyester type initiator such as monobutyl peroxybenzoate is used as a high temperature initiator. The thermal decomposition temperatures of these initiators in cumene are approximately 75°C and 105' at the 10 hour half-life temperature, respectively.
It is C. By using these initiators in combination and carrying out the polymerization while raising the polymerization temperature stepwise, a high molecular weight polymer can be obtained without reducing the polymerization rate.

On the other hand, polymers are usually molded using processing machines such as extruders, but if the melt viscosity of the polymer is too high, there is a problem that molding cannot be performed.

Therefore, there is a need for polymers that have good mechanical properties and are easy to mold.

(Problems to be Solved by the Invention) Organic peroxides used as polymerization initiators also have the property of causing crosslinking or molecular cleavage (cleavage) of polymers. Therefore, in the latter half of the polymerization, while a relatively large amount of vinyl monomer remains (probably 1z or more), crosslinking of the polymer mainly occurs preferentially. It is also believed that cleavage occurs preferentially when the remaining monomer becomes extremely small.

Crosslinking of polymers increases melt viscosity and reduces processability. Furthermore, it is known that cleavage of a polymer lowers the molecular weight and mechanical strength, and also causes unsaturated bonds to be formed at the terminals of the polymer, resulting in a decrease in heat resistance stability.

(Means for Solving the Problems) As a result of long-term research into the problems of the above-mentioned conventional methods, the present inventors found that by using a specific polymerization initiator, the cross-linking reaction and cleavage in the late stage of polymerization were improved. The present invention was completed by discovering a method for obtaining a polymer with a small amount of carbon.

That is, in the method of the present invention, 1,1-dimethylbutylperoxyisopropyl carbonate, 1,1-dimethylpropylperoxyisopropyl carbonate, 1,1-dimethylbutylperoxyisopropyl carbonate, 1,1-dimethylbutylperoxyisopropyl carbonate, A vinyl monomer characterized in that one or more members selected from the group consisting of vinyl carbonate, pinanyl peroxyisopropyl carbonate, and 1,1°3.3-tetramethylbutylperoxyisopropyl carbonate are used as a polymerization initiator. It is a method of polymerization of the body.

Examples of vinyl monomers used in the present invention include ebastyrene, α-methylstyrene, acrylonitrile, acrylic esters, methacrylic esters, maleic esters, fumaric esters, maleimides, butadiene, and vinyl acetate. etc.

In addition to these monomers, various chain transfer agents, rubber components, or blowing agents such as pentane may be added.

The polymerization initiators used in the present invention include 1.1-dimethylbutylperoxyisopropyl carbonate, 1.1-dimethylpropylperoxyisopropyl carbonate,
pinanyl peroxyisopropyl carbonate and 1.
One type or two or more types of the group consisting of 1.3.3-tetramethylbutylperoxyisopropyl carbonate may be used in combination. Further, as mentioned above, it may be used in combination with other initiators having different thermal decomposition temperatures.

The amount of initiator added varies depending on the type of monomers used for polymerization or their combination, but in general, the amount of monomers added is 100
The amount is from o, ooi to 5 parts by weight, preferably from 0.01 to 0.5 parts by weight, in terms of pure product. When the amount is 0.001 parts by weight, the polymerization rate tends to be slow. Moreover, if it exceeds 5 parts by weight, it is not economical (and undesirable).

The polymerization method used in the present invention is a conventional bulk polymerization, solution polymerization, or suspension polymerization method, and the polymerization temperature is generally 60°C.
-150°C, preferably in the temperature range of 80-130°C. The polymerization temperature is a constant temperature or a relatively low temperature in the initial stage of polymerization, and a method is used in which the temperature is raised stepwise as the polymerization progresses.

The polymers obtained in the present invention are GP type polystyrene, impact polystyrene, expanded polystyrene, polymethyl methacrylate, styrene/acrylonitrile copolymer, styrene/acrylonitrile/
Phenylmaleimide copolymer, butyl methacrylate/2
- Copolymers of various acrylic acids or methacrylic esters such as ethylhexyl methacrylate copolymers.

(Effects of the Invention) The present invention, which uses a specific polymerization initiator, has the following characteristics.

That is, the present invention significantly reduces crosslinking or cleavage of the polymer in the latter half of polymerization compared to conventional initiators. The melt viscosity of the resulting polymer was reduced. Additionally, the thermal stability of the polymer was improved.

The polymerization initiator used in the present invention has a high ability to initiate polymerization, and the initiator itself or its decomposition products do not cause coloring and are not harmful compounds to humans or animals.

(Example) Hereinafter, the present invention will be specifically explained with reference to Examples.

In addition, the abbreviations of initiators used in the examples mean the following compounds.

Am-1; 1,1-dimethylpropylperoxyisopropyl carbonate) tex-1i 1,1-dimethylbutylperoxyisopropyl carbonate Pi-1; Vinanylperoxyisopropyl carbonate 0c-1; 1,1,3.3-tetra Methyl butyl peroxyisopropyl carbonate Bu-1; i+1-dimethylethyl peroxyisopropyl carbonate BPO; benzoyl peroxide Bu-Z; t-butyl peroxybenzoate The molecular weight of the product obtained by polymerization was determined by gel permeation chromatography (GPC). ) was measured in terms of polystyrene.

Examples 1-4 and Comparative Examples 1-3 10 g of styrene and the initiator shown in Table 1.2 were added to a glass ampoule of 20 volumes.

The ampoule was vacuum degassed, then melted and sealed.

This was polymerized in a constant temperature oil bath at the temperatures shown in Tables 1 and 2 for 10 hours. Thereafter, the ampoule was transferred to a constant temperature bath at 250°C and heated for 1 hour.

Every 2 hours of polymerization, the final polymerized product was poured into methanol for reprecipitation. The polymerization conversion rate was calculated from the weight of the obtained white powder. Also, by GPC, the weight average molecule ffl (hw
) was measured. Further, the MI value was separately determined using a melt flow indexer for a sample with a conversion rate of 100%. The respective results are shown in Table 1.2.

Example 5 Methyl methacrylate Log using the same ampoule as in Example 1 and 1,1.3.3-tetramethylbutylperoxyisopropyl carbonate 0.003 as initiator.
mol/4 was added and polymerized at 105°C. The same analysis as in Example 1 was performed. The conversion rate was 63.5% after 2 hours of polymerization and 100% after 4 hours. The weight average molecular weight at 80% conversion is 526,000, and at 100% conversion is 768.
It was 000. Also, after heating at 250°C for 11 hours, 7
It was 23,000.

Comparative Example 4 0 benzoyl peroxide as initiator in Example 5
．． 004 n+ol/j! The same operation as in Example 5 was carried out except that the polymerization temperature was changed to 90°C. The conversion rate was 48.3% after 2 hours of polymerization and 100% after 4 hours.

The weight average molecular weight at a conversion rate of 80% is 499,000,
Conversion rate 100% Teha 931000.4 after heating for 1 hour
It was 20,000.

Example 6 In a stainless steel autoclave with a capacity of 1500 mfl,
200 ml of ion exchange water and polyvinyl alcohol O,
tg and dissolved. Then, 30 g of α-methylstyrene, 20 g of acrylonitrile and 50 g of styrene
and 0.03 mol/1,1,3.3-tetramethylbutylperoxyisopropyl carbonate as an initiator.
1 was added and the space was replaced with nitrogen, followed by polymerization at 105°C.

The same analysis as in Example 1 was performed. 31. with polymerization time of 2 hours.
The conversion rate was 5%, 68.0% in 4 hours, and 99.1% in 6 hours. The weight average molecular weight at a conversion rate of 80% is 3
75,000, and 411,000 at a conversion rate of 99.1%. Moreover, after heating at 250°C for 11 hours, it was 391,000.

Comparative Example 5 0 benzoyl peroxide as initiator in Example 6
．． The same operation as in Example 6 was performed except that 05 mol/l was used and the polymerization temperature was changed to 90°C. Polymerization time: 28.5% at 2 hours, 71.1% at 4 hours, 9844% at 6 hours.
The conversion rate was . The weight average molecular weight at a conversion rate of 80% is 312,000. At 100% conversion rate, it is 435,000.
Moreover, it was 329,000 after heating at 250°C for 1 hour.

As is clear from the above Examples and Comparative Examples, the method of the present invention can provide a polymer without crosslinking or cleavage in the late stage of polymerization. As a result, the melt viscosity of the polymer was reduced and processability was improved.

It also improved thermal stability.

For example, when looking at the molecular weight at a polymerization conversion rate of 80% and 100% as shown in Examples 1 to 4 and Comparative Examples 1 to 3 of the initiator,
In the comparative example, the difference was large, indicating that the molecular weight was increased by the crosslinking reaction.

Also, the MI value was relatively large in the comparative example.

Also, when looking at the molecular weights at polymerization conversion rates of 80% and 100% in Example 5 and Comparative Example 4, and Example 6 and Comparative Example 5, there is a large difference in the molecular weight in Comparative Example, indicating that the molecular weight has increased due to the crosslinking reaction. Indicated.

Claims (1)

[Claims] 1. When polymerizing a vinyl monomer alone or a mixture with a vinyl monomer copolymerizable with it, 1,1-dimethylbutylperoxyisopropyl carbonate, 1,1
- Vinyl characterized in that one or more of the group consisting of dimethylpropylperoxyisopropyl carbonate, pinanylperoxyisopropyl carbonate and 1,1,3,3-tetramethylbutylperoxyisopropyl carbonate is used as a polymerization initiator. Monomer polymerization method.