JPH0232108A - Production of copolymer - Google Patents

Abstract

PURPOSE:To easily obtain a high-molecular weight copolymer useful as a toner for electrophotography by copolymerizing styrene monomer and an unsaturated ester monomer in the presence of a specific tetrafunctional organic peroxide as a polymerization initiator. CONSTITUTION:The objective copolymer is produced by copolymerizing a mixture of styrene monomer, an unsaturated acid ester (e.g., methyl acrylate) and optionally a monomer copolymerizable therewith in the presence of an organic peroxide of formula (R is 1-5C alkyl or phenyl; R1 and R2 are 1-2 alkyl) as a polymerization initiator. The compound of formula is e.g., 2,2-bis(4,4-di-t- butylperoxycyclohexyl)propane. The amount of the compound of formula is preferably 0.05-3.5wt.% based on the total amount of the monomers and the polymerization reaction temperature is preferably 80-125 deg.C.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention provides a method for producing a high molecular weight copolymer used in an electrophotographic toner, in which a tetrafunctional organic peroxide having a specific structure is used as a polymerization initiator. This invention relates to an industrially viable copolymerization method using a material.

(Problems to be Solved by Prior Art and Inventions) Recently, the characteristics of electrophotographic resins have been improved based on the demand for low-temperature fixing properties in order to reduce power consumption in response to household and high-speed models. There are high expectations for low molecular weight resins. However, although using only a low molecular weight resin does improve the fixing properties, it has the disadvantage of poor blocking properties, and a high molecular weight resin is absolutely essential in order to maintain the offset property. Therefore, in order to satisfy the minimum characteristics of fixing properties, offset properties, and blocking properties, a resin is required that exhibits a molecular weight distribution that simultaneously contains a low molecular weight portion and a high molecular weight portion. In other words, resins with a wide molecular weight distribution are preferred. Regarding the production of high molecular weight resins, conventional methods have been adopted in which the amount of polymerization initiator added is suppressed and polymerization is performed under relatively low temperature conditions, but the drawbacks of this method are:
The polymerization time is inevitably long and it is not economical. In recent years, certain bifunctional organic peroxides have been used in some cases as a method for improving this, but it is not easy to obtain the desired high molecular weight resin, and there are no industrially simple and effective methods. The emergence of polymerization treatment was hoped for.

(Means for Solving the Problems) In order to obtain a high molecular weight resin suitable for such toner resins, as a result of intensive studies from the viewpoint of using various types of organic peroxides as effective polymerization initiators, we found that It has been found that a high molecular weight resin for toners can be obtained very effectively by using a polyfunctional organic peroxide having the following, leading to the present invention.

That is, in the present invention, when copolymerizing a mixture of a styrene monomer and an unsaturated acid ester monomer or at least one monomer selected from the group of monomers copolymerizable with these monomers, the general formula This is a method for producing a copolymer using an organic peroxide represented by (I).

(In the formula, R represents an alkyl group having 1 to 5 carbon atoms or a phenyl group, and R and R represent an alkyl group having 1 to 2 carbon atoms.)

In the present invention, the tetrafunctional organic peroxide having the specific structure represented by the general formula (1), that is, Burketals, includes 2.2-bis(4,4-di-t-butylperoxycyclohexyl)propane 2 .2-bis(414-di-t-amylperoxycyclohexyl)propane 2,2-bis(4,4-di-L-octylperoxycyclohexyl)propane 2,2-bis(4,4-di-α- An example is cumylperoxycyclohexyl)propane, 2,2-bis(4,4-di-t-butylperoxycyclohexyl)butane, and 2,2-bis(4,4-di-t-octylperoxycyclohexyl)butane. These barketals are
It can be synthesized relatively easily based on the production methods described in Japanese Patent Publication No. 19013-19013 and Japanese Patent Publication No. 19511-1983. That is, a diketone compound R1K represented by the following general formula (■).

(Here, R and R1 are as defined in the general formula (I) above.) Tertiary hydroperoxides, such as t-butyl hydroperoxide, t-amyl hydroperoxide, t-octyl hydroperoxide , cumene hydroperoxide, etc., in the presence of an acid catalyst such as sulfuric acid.

The amount of the tetrafunctional organic peroxide represented by the general formula (1) used as a polymerization initiator is O, O
S weight% to 3.5% by weight is preferred.

If it is less than 0.05% by weight, the polymerization conversion rate will not increase and it is not practical. On the other hand, if it is more than 3.5% by weight, the polymerization rate will generally increase significantly, making it difficult to control the polymerization reaction.

The organic peroxide of the present invention can be used in combination of two types, or can be used in combination with other organic peroxides other than the organic peroxide represented by the general formula (I), and even in azo polymerization. It can also be used in combination with an initiator.

In order to obtain a high polymerization conversion rate and high molecular weight copolymer with a small amount of residual monomer, it is preferable to conduct the polymerization at a temperature range of 80°C or higher and lower than 125°C. A polymerization method can also be adopted. In addition, when polymerizing in a temperature range below 80℃, the conversion rate increases and 1
In polymerization at 25° C. or higher, it becomes difficult to control the reaction.

The monomers used in the present invention consist of styrene monomers and unsaturated acid ester monomers, and if necessary, monomers copolymerizable with these monomers may be added to the styrene monomers. Preferably 90 to 50% by weight, preferably 10 to 50% by weight of unsaturated acid ester monomers, and preferably 0 to 20% by weight of copolymerizable monomers. Unsaturated acid ester monomers include methyl acrylate, ethyl acrylate,
1so-propyl acrylate, n-butyl acrylate,
2-ethylhexyl acrylate, methyl methacrylate,
These include ethyl methacrylate, 1so-7' methacrylate, n-butyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, and the like. Furthermore, the monomer groups that can be copolymerized with these include unsaturated acids such as acrylic acid and methacrylic acid, unsaturated acid derivatives such as acrylonitrile, methacrylonitrile, and acrylamide, conjugated dienes such as butadiene and isoprene, and α- Examples include methylstyrene and vinyltoluene.

The polymerization method may be either a suspension polymerization method or a bulk polymerization method, but other solution polymerization methods can also be applied.

(Example) Next, the present invention will be explained with reference to Examples, and the polymerization results are summarized in Table 1. Prior to explaining the examples,
The polymerization method and the evaluation method of the copolymer will be explained below.

Polymerization method Polymerization was carried out using a brown ampoule with an internal volume of 3 cc.

That is, a predetermined amount of styrene (hereinafter abbreviated as 3T), n-butyl acrylate (hereinafter abbreviated as BA), and respective polymerization initiators were placed in a pre-washed ampoule, and after performing a purging operation with nitrogen gas, Melted and sealed.

0, which was polymerized for a predetermined time in an oil bath set at a predetermined temperature.
After the polymerization was completed, the ampoule was taken out and rapidly cooled. The contents were taken out as necessary and subjected to respective evaluations after pretreatment.

Note that the amount of the polymerization initiator added is expressed in weight % (in terms of pure product), and expressed in terms of total monomer amount versus weight. The st/BA charging ratio was expressed as a weight ratio.

Copolymer evaluation method/Copolymer conversion rate (%): Calculated backward from the measurement results of residual st and BA amount by gas chromatography.

・Molecular it (Hw, mn, 'F1w/'Ftn);
A spear IM was made using standard polystyrene and measured using the GPC method.

Examples 1 to 6 Bulk polymerization of st/BA system Polymerization was carried out under the polymerization conditions shown in Table 1 and according to the above polymerization method using a peroxide as a polymerization initiator.

Comparative Examples 1 to 4 st/BA-based bulk polymerization Polymerization was carried out according to the polymerization conditions shown in Table 1 and the polymerization method described above, using various organic peroxides as polymerization initiators.

The characteristic values of the copolymers obtained in Examples 1 to 6 and Comparative Examples 1 to 4 are collectively shown in Table 1.

As is clear from Table 1, the physical properties of the copolymers of the l-functional, di-functional, and tri-functional organic peroxides in the comparative example are all due to the specific tetra-functional organic peroxide of the present invention. It is inferior to copolymers (both molecular weight and conversion rate). Furthermore, the results of all the examples show that high conversion rates and high molecular weight copolymers can be obtained with short polymerization times.

Example 7 Suspension polymerization of st/BA system 400 g of a 1.5% by weight polyvinyl alcohol (85% saponified product) aqueous solution was charged into an autoclave equipped with a stirrer in No. 11, and st16Qg, B^40g, 2.
A mixed solution of 6 g of 2bis(414-di(-butylperoxycyclohexyl)propane) was introduced, and the mixture was polymerized at 90°C for 2 hours, at 100°C for 2 hours, and at 120°C for 2 hours, followed by cooling, washing, dehydration, A copolymer was obtained by drying.As a result, the conversion rate of the copolymer was 99.8%, and the weight average molecule!
(Nw) is 432,000, number average molecular weight (Tn) is 1
8000, and Mw/L was 24.0.

Comparative Example 5 Polymerization to st/B 8-type polymerization In place of 2,2-bis(44-di-t-butylperoxycyclohexyl)propane, 1.
A copolymer was obtained in the same manner as in Example 7 except that 1-di-t-butylperoxy3.3.5-trimethylcyclohexane was used. As a result, the conversion rate of the copolymer i; t98.
1%, K- is 238,000, Hn is 14,000, Mw/
rn was 17.0.

(Effects of the Invention) The specific organic peroxide of the present invention is a so-called tetrafunctional type having four peroxy bonds in one molecule, that is, four polymerization initiation sites. When polymerization is carried out using conventional 1.2- and 3-functional polymerization initiators, polymerization initiation occurs in multiple groups and propagation reactions also occur in multiple groups in one molecule, so the copolymer obtained as a result of the termination reaction A copolymer with a higher molecular weight can be obtained compared to the above. That is, according to the present invention, it is easier to produce a copolymer having a higher molecular weight than a copolymer produced using a conventional polymerization initiator, and its industrial application range is wide and valuable.

Patent applicant: Kayaku Nouri Co., Ltd.

Claims (1)

[Claims] In copolymerizing a mixture of a styrene monomer and an unsaturated acid ester monomer or at least one monomer selected from the group of monomers copolymerizable with these monomers, A method for producing a copolymer, characterized by using an organic peroxide represented by formula (I). ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (I) (In the formula, R represents an alkyl group having 1 to 5 carbon atoms or a phenyl group, and R_1 and R_2 represent an alkyl group having 1 to 2 carbon atoms.)