JPH0576486B2 - - Google Patents

Description

[Detailed description of the invention]

[] Industrial Application Field The present invention relates to a method for producing an acrylic copolymer. More specifically, the present invention relates to a method for producing an acrylic copolymer having excellent transparency and mechanical strength. [] Conventional technology and problems Methyl methacrylate polymer has excellent transparency and weather resistance, and is widely used as cast boards, extruded boards, various injection molded products, etc., regardless of whether they are used indoors or outdoors. However, it has the disadvantage that it is extremely brittle and cannot be used in its original form, especially for applications such as relatively thin sheets, films, and molded products. It is common to use rubber-elastic polymers as a way to improve the brittle properties of rigid thermoplastic resins, not limited to methyl methacrylate polymers, which have high hardness and rigidity, especially in the presence of rubber-like elastic bodies. Many methods of graft polymerization have been proposed. Regarding methyl methacrylate-based polymers, for example, in the presence of a cross-linked acrylic ester-based rubber-like elastic body, graft polymerization is carried out sequentially in multiple stages by changing the mixing ratio of methyl methacrylate and acrylic ester. Method (Tokuko Showa 52-
14269, JP-A No. 48-43444, etc.), and a method of graft polymerization by continuously adding acrylic esters and methacrylic esters in the presence of an elastic polymer (Japanese Patent Publication No. 48-36947) ), etc. These methods focus on optimizing the composition, degree of crosslinking, or particle size of the rubbery elastic body, while others focus on optimizing the composition, degree of grafting (chemical bond There are two main types of methods: methods of graft polymerization, compatibility between the rubber-like elastic body part and the resin phase part to be grafted, and methods of optimizing the bonding state. They are the same in that it is important that a tight bond be formed between the rubber-like elastic body and the resin phase portion. However, in the polymerization process of these methods, which are called graft polymerization methods, the resin phase portion that is graft-polymerized with the rubber-like elastic material (or the resin phase that is soft and polymerized to avoid too much difference in composition from the rubber-like elastic material) is used. It is generally difficult to show whether or not the degree of chemical bonding with the mesophase portion (which is designed to contain a relatively large amount of monomer components) is sufficient.
It is said that the graft polymerization method is effective in increasing the degree of chemical bonding between two phases with different properties and increasing the compatibility of both phases, but the grafting reaction of the liver and kidneys is not satisfactory. The reality is that it is not clear whether this is being done to the extent that it could be done. Transparency and mechanical strength generally contradict each other and are difficult to balance. However, the balance between transparency and mechanical strength of acrylic graft copolymers improved by the graft polymerization method has not necessarily reached a satisfactory level. I can't say that it is. In view of these facts, the present inventors believe that the problems with the graft copolymerization method are the insufficient degree of chemical bonding between the rubber-like elastic body and the resin phase portion or the above-mentioned intermediate phase portion, and the compatibility of each portion. As a result of intensive study, we have arrived at the present invention, believing that this is due to the insufficiency of the above. [] Means for Solving the Problems The present invention provides (A) methyl methacrylate or a mixture of methyl methacrylate containing an ethylenically monounsaturated monomer in an amount of 10% by weight or less (hereinafter referred to as monomer (A)), 50 to 90 parts by weight; (B) An ester of a monohydric alcohol having 1 to 8 carbon atoms and acrylic acid or methacrylic acid, containing acrylic monomers excluding methyl methacrylate. 1 type or 2 or more types (hereinafter referred to as monomer (B)), 10 to 50 parts by weight; and (C) 1 type or 2 or more types of ethylene-based polyfunctional monomers (hereinafter referred to as monomer (C) In emulsion copolymerizing 0.005 to 3 parts by weight of 0.005 to 3 parts by weight, the polymerization system is In this supply mode, monomer (A), monomer (B), and monomer (C) are supplied simultaneously, and all of the monomer (A) at the time of the start of supply is The proportion of monomer in the monomer is 8 to 35% by weight, and monomer (B) and monomer (C) are supplied by continuously reducing the amount added per unit time as the supply time passes. At the time of completion, the amount added should be zero, and the monomer (B)
The present invention relates to a method for producing an acrylic copolymer, characterized in that the supply of the monomer (C) is carried out within the period of supply of the monomer (A). The monomer (A) used in the present invention is in the range of 50 to 90 parts by weight, and the monomer (B) is in the range of 10 to 50 parts by weight. If the amount of monomer (A) is less than 50 parts by weight, the resulting copolymer will have a low softening temperature and a decrease in hardness and tensile properties, which is not preferable. Also, the amount of monomer (A) is 90
Exceeding the weight part is not preferable because it becomes brittle and has low impact strength. Preferably, the monomer (A) is 60 to
80 parts by weight, and 20 to 40 parts by weight of monomer (B). The method for supplying each monomer to the polymerization system is as described below. Monomer (A) is added starting from the start of polymerization, and the amount added at that point is in the range of 8 to 85% by weight based on the total amount of monomers supplied. If the amount added at the start of supply of monomer (A) is less than 8% by weight, the stability of polymerization will deteriorate, the particle size of the obtained copolymer will tend to increase, and transparency will decrease. On the other hand, if it exceeds 35% by weight, the impact strength will decrease. The amount of monomer (A) added at each moment is determined from the designed amount to be included in the final copolymer, the length of the designed supply period, and the designed amount added at the time of starting the supply. Generally, it is practical to express the amount added as a function of polymerization time, and to adjust the amount actually added based on the integral value of an interval of about 5 minutes using an integral expression of the function. Further, as one embodiment, it is also possible to keep the amount of monomer (A) added per unit time constant. There is no particular limit on the supply time of monomer (A), but considering the reactivity with monomer (B), the cumulative supply ratio of monomer (A) and monomer (B) and the production In order not to cause a large difference between the monomer composition ratio in the copolymer to be processed and to prevent an increase in the amount of unreacted monomers with low reactivity, the heat removal capacity of the polymerization tank, An arbitrary value can be determined by taking into consideration the capacity of the addition equipment, economic efficiency, etc. On the other hand, the monomer (B) is added from the beginning of polymerization, and the amount added at each moment is continuously decreased as the elapsed time of feeding increases, and at the end of the feeding, the amount added is so that it becomes zero (this includes cases where it becomes zero before the end of supply). Further, the monomer (B) is supplied within the monomer (A) supply period. However, if the supply period of monomer (B) is too short, the stability of polymerization tends to deteriorate and transparency tends to be impaired.
It is best to set the supply period to be at least 1/8 of the length of the monomer (B) supply period. Conversely, if the supply end time of monomer (B) is set after the supply end time of monomer (A), the impact strength will be lowered and softened. Since the temperature also tends to decrease, the supply of monomer (B) should be finished at the same time as the supply of monomer (A) or earlier. Monomer (B) from moment to moment
The amount of addition is based on the designed amount to be included in the final copolymer, the length of the designed supply period, the designed amount to be included in the final copolymer, and the monomer at the time of starting supply. It is determined by the design ratio of (A) and monomer (B) as a function of the supply elapsed time starting from the addition start point, and the addition amount is adjusted in the same way as for monomer (A). . In the present invention, monomers other than methyl methacrylate that constitute the monomer (A) component include aromatic vinyl compounds such as styrene, vinyltoluene, and α-methylstyrene, methyl acrylate, ethyl acrylate, and acrylic acid. Acrylic acid esters such as propyl acid, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, glycidyl acrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, etc. and methacrylic acid esters such as ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, glycidyl methacrylate, acrylic acid, methacrylic acid, acrylic acid or methacrylic acid. Alkali metal salts, amides of acrylic acid or methacrylic acid such as acrylic acid amide, methacrylic acid amide, dimethylaminoacrylamide and their nitrogen-substituted compounds, unsaturated nitrile compounds such as acrylonitrile and methacrylonitrile, vinyl acetate, vinyl propionate, etc. vinyl esters, halogenated vinyl compounds such as vinyl chloride, vinylidene chloride, and vinylidene compounds. Preferred are aromatic vinyl compounds, acrylic esters, and methacrylic esters. These monomers are usually 10% by weight relative to methyl methacrylate.
Hereinafter, preferably an amount of 8% by weight or less is used. In the present invention, the acrylic esters and methacrylic esters (excluding methyl methacrylate) constituting the monomer (B) are those in which the number of carbon atoms in the alkyl group ranges from 1 to 8, such as methyl acrylate, acrylic Acrylic acid esters such as ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-hexyl acrylate, cyclohexyl acrylate, n-octyl allylate, 2-ethylhexyl acrylate, etc. , ethyl methacrylate,
Examples include methacrylic acid esters such as n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-hexyl methacrylate, cyclohexyl methacrylate, and 2-ethylhexyl methacrylate. The optimum amount of the monomer (C) used in the present invention generally varies depending on its molecular weight, the number of functional groups in the molecule, the reactivity of the functional groups, etc., but it ranges from 0.005 to
It is used in an amount of 3 parts by weight, preferably 0.01 to 2.5 parts by weight. Even if the amount of monomer (C) is less than 0.005 parts by weight or conversely exceeds 3 parts by weight, the impact strength and transparency of the resulting copolymer are reduced. Further, the timing of addition of monomer (C) is the same as the period of supply of monomer (B), and specifically, it is preferable to mix it with monomer (B) in advance and add it. Examples of the ethylene-based polyfunctional monomer constituting the monomer (C) include diallyl esters of divalent carboxylic acids such as diallyl succinate, diallyl phthalate, diallyl adipate, diallyl maleate, and diallyl fumarate; Allyl esters of acrylic acid or methacrylic acid, diacrylic esters or dimethacrylic esters of dihydric alcohols such as mono- or polyethylene glycol, propylene glycol, 1,4-butanediol, 1,10-decanediol, 1,10 Divinyl ethers such as -decanediol divinyl ether and 1,12-octadecanediol divinyl ether, divinylbenzene, triallyl cyanurate, triallyl isocyanurate, trimethylolpropane trimethacrylate, and the like. Preferred are diallyl esters of dihydric carboxylic acids, diacrylic esters or dimethacrylic esters of dihydric alcohols. It is also possible to use a chain transfer agent in the present invention, and those commonly used in the polymerization of acrylic esters, methacrylic esters, etc. can be used. Examples include alkyl mercaptans such as octyl mercaptan and dodecyl mercaptan, n-butyl thioglycolate, octyl thioglycolate, thioglycolic acid, thiophenol, and mercaptoethanol. There is no particular limit, but the amount of chain transfer agent used is preferably in the range of 0.05 to 1.5% by weight based on monomer (A). Monomer (B) is supplied together with monomer (A). It is desirable to adjust the timing of addition and reduce the amount as much as possible, such as by adding later. As the polymerization initiator used in the present invention, those generally used for emulsion polymerization of acrylic esters or methacrylic esters are used. For example, water-soluble initiators such as potassium persulfate and ammonium persulfate, water-soluble redox initiators such as hydrogen peroxide-Rongalite type, potassium persulfate and sodium thiosulfate type, or cumene hydroperoxide-sodium bisulfate type, etc. oil-soluble redox initiator systems and the like. The emulsifier used in the present invention may be one commonly used in emulsion polymerization of acrylic ester or methacrylic ester, such as alkali metal soaps such as sodium oleate and potassium stearate, and alkylbenzene sulfonates such as sodium dodecylbenzenesulfonate. Anionic emulsifiers such as dialkyl sulfosuccinates such as sodium dibutyl sulfosuccinate and sodium dioctyl sulfosuccinate, alkyl sulfates such as alkyl diphenyl ether disulfonates, and sodium lauryl sulfate are used, and two or more of these may be used in combination. is also possible. Furthermore, it is also possible to use a small amount of a nonionic emulsifier or a cationic emulsifier as an emulsion stabilizing aid. It is also common practice to add part of the emulsifier in portions as the polymerization progresses in order to adjust the particle size of the resulting copolymer; however, these methods may also be used in the present invention. is possible. Although the mechanism of the present invention is not clear, the process of producing a copolymer part exhibiting rubber-like elasticity and the process of producing a copolymer part having rigidity are carried out continuously from start to finish, so that graft copolymerization is possible. As in the case, there is no gap between the process of forming the rubber-like elastic body part and the polymerization process of the resin phase part or the intermediate phase part, so there is no clear boundary between the elastic part and the rigid part. It is presumed that the two parts are easily integrated due to their compatibility, and the brittleness is significantly improved without significantly impairing the excellent transparency of the methyl methacrylate polymer. [] Examples The present invention will be described below with reference to Examples, but the present invention is not limited to these Examples. Example 1 Pour 50 g of deionized water into a 100 g autoclave, perform nitrogen bubbling for 10 minutes, and add 200 g of sodium dibutyl sulfosuccinate and 60 g of potassium persulfate.
g was added, the tank was sealed, and the internal space of the tank was replaced with nitrogen, and then stirring was started to raise the internal temperature. After reaching 70℃, add 13Kg of methyl methacrylate [975t+
At the same time, the supply of butyl acrylate (7 kg) to the autoclave was started according to the addition amount expressed as [-2240t+5600]. In addition, t in the formula in [ ] above represents the elapsed time (hr) starting from the start of addition,
The unit of the amount added expressed in [ ] is weight (g). Further, the amount of addition was adjusted by changing the conditions based on the integrated amount of addition every 1.2 minutes. The total addition time of butyl acrylate was 2.5 hours, and 100 g of allyl methacrylate was uniformly dissolved in butyl acrylate in advance. On the other hand, methyl methacrylate was supplied alone for a period of 2.5 hours from the start of addition, and the remaining methyl methacrylate was supplied over 1.5 hours as a mixture in which 75 g of octyl thioglycolate was uniformly dissolved. After that, stirring was continued at the same temperature for 1 hour. Subsequently, while stirring, the internal temperature was raised to 85°C, and after reaching 85°C, stirring was continued for an additional hour to complete the polymerization. Table 1 shows the physical properties of the resin sampled during the polymerization process. 210 deionized water was added to the obtained resin dispersion, and while keeping the temperature at 80°C with stirring, a 2% aluminum chloride aqueous solution was gradually added dropwise to perform salting out.
It was cooled, dehydrated, and dried to obtain 19.6 kg of resin. Table 2 shows the mechanical strength and optical properties of sheets press-molded from excellent resin at 210°C. Example 2 19.6 kg of resin was produced in exactly the same manner as in Example 1, except that 60 g of Latemul ASK [special carboxylic acid type emulsifier (manufactured by Kao Soap Co., Ltd.]) was used as an emulsifier instead of sodium dibutyl sulfosuccinate. Obtained. Table 1 shows the physical properties of the sample taken during the polymerization, and Table 2 shows the physical properties of the resin press sheet obtained. Comparative Example 1 19.5 kg of resin was obtained in the same manner as in Example 1, except that the addition rate of butyl acrylate was kept constant and the amount of addition was expressed as [0t+2800].
Table 1 shows the physical properties of the resin sampled during the polymerization, and Table 2 shows the physical properties of the pressed sheet of the resin obtained. Comparative Example 2 A 100ml autoclave was charged with 50ml of deionized water, and nitrogen bubbling was performed for 10 minutes, followed by 150g of sodium dioctyl sulfosuccinate, 60g of potassium persulfate, 20kg of butyl acrylate, and 280g of allyl methacrylate, and the autoclave was sealed and replaced with nitrogen. I went. Elevating the temperature and stirring were started, and the internal temperature was maintained at 70°C for 3 hours, and then raised to 85°C and reacted for an additional 1 hour to prepare a butyl acrylate polymer. Charge 29.3 of deionized water into another autoclave and perform nitrogen purge, then add 20.7 of the previously prepared butyl acrylate polymer latex and 40 g of potassium persulfate, and after sealing, purge the space with nitrogen.
The temperature was increased and stirring was started. After the internal temperature reaches 70℃,
According to the addition amount expressed as 13Kg of methyl methacrylate [2889t+0], and 1Kg of butyl acrylate.
, the supply time is 1 hour, [−2000t+
2000], the supply to the autoclave was started at the same time. The amount added was adjusted in the same manner as in Example 1. Also, from the start of supply, 1
After that time, 75 g of octyl thioglycolate was uniformly mixed with the remaining methyl methacrylate, and the addition was continued for an additional 3 hours. The temperature was maintained at 70°C for 1 hour after the monomer supply was completed, and then the temperature was raised to 85°C.
The reaction was continued for an additional hour to complete the polymerization. The physical properties of the resin sampled during the polymerization were as shown in Table 1. Table 2 shows the physical properties of a dried resin press sheet obtained by treating the obtained resin dispersion in the same manner as in Example 1. Comparative Example 3 Fill an autoclave with 29.3 ml of deionized water,
Nitrogen bubbling was carried out, 20.7 g of the butyl acrylate polymer latex prepared in Comparative Example 2 and 5 g of potassium persulfate were added, and after sealing and purging with nitrogen, heating and stirring were started. After the internal temperature reached 70°C, a mixture of 800 g of butyl acrylate and 200 g of methyl methacrylate was gradually added over 30 minutes.
The reaction was continued for an additional 30 minutes. Then 5 g of potassium persulfate (5% aqueous solution) was added, and a mixture of 200 g of butyl acrylate and 800 g of methyl methacrylate was gradually added over 30 minutes.
The reaction was continued for an additional 30 minutes. Followed by potassium persulfate 40
(as a 5% aqueous solution) and a mixture of 12 Kg of methyl methacrylate and 75 g of octyl thioglycolate was added at a constant rate over 2 hours. Thereafter, the temperature was raised to 85°C and maintained for 1 hour to complete the polymerization. Table 1 shows the physical properties of the resin sampled during the polymerization, and Table 2 shows the physical properties of the press sheet of the resin finally obtained. Comparative Example 4 A resin was obtained in exactly the same manner as in Comparative Example 2 except that 70 g of sodium lauryl sulfate was used in place of sodium dioctyl sulfosuccinate. Table 2 shows the physical properties of the obtained resin press sheet.

【table】

[Table] Example 3 In Example 1, the amount of methyl methacrylate used was changed to 12.35 kg, and the amount of ethyl acrylate was changed to 0.65 kg.
A resin was obtained in the same manner except that Kg was used in combination and the amount of octyl thioglycolate was 15 Kg.
Table 3 shows the pressed sheet physical properties of the obtained resin. Example 4 In Example 1, the supply time of butyl acrylate was set to 3.5 hours, and the addition amount was adjusted to [-1142.9t+
A resin was obtained in exactly the same manner except that the same procedure was used for [4000]. The press sheet physical properties of the obtained resin were measured in the third
Shown in the table. Example 5 In Example 1, the supply time of butyl acrylate was set to 3 hours, and the addition amount was adjusted to [-388.9t ² +
3500] was done in exactly the same way except for what was done with [3500].
Table 3 shows the pressed sheet physical properties of the obtained resin. Example 6 In Example 1, the amount of methyl methacrylate used was 5 kg and the amount added was adjusted to [1125t + 1500], the amount of butyl acrylate used was 5 kg and the amount added was adjusted to [-1600t + 4000], Resins were obtained in the same manner except that the amount of allyl acid used was 71.4 g or the amount of octyl thioglycolate was 86.5 g. Table 3 shows the pressed sheet physical properties of the obtained resin. Example 7 In Example 1, the amount of sodium dibutyl sulfosuccinate used was changed to 300 g, the amount of methyl methacrylate used was changed to 12.4 Kg, and the amount added was adjusted to [-62t + 3224] to use butyl acrylate, etc. Adjust the amount to 7.6Kg [-11400t+
11400] and the supply time was set to 1 hour.
A resin was obtained in the same manner except that 114 g of diallyl maleate was used instead of allyl methacrylate, and dodecylmercabutane was used instead of octyl thioglycolate, and the amount used was 87 g. Table 3 shows the physical properties of the obtained resin press sheet.

[Table] [Effects of the Invention] As is clear from the above, the production method of the present invention has produced an acrylic material with an excellent balance between transparency and strength, in which physical properties such as impact strength have been significantly improved without a decrease in transparency. copolymers are provided.

Claims (1)

[Scope of Claims] 1 (A) Methyl methacrylate or a mixture of methyl methacrylate containing an ethylenically unsaturated monomer in an amount of 10% by weight or less (hereinafter referred to as monomer)
(A)), 50 to 90 parts by weight (B) An ester of a monohydric alcohol having 1 to 8 carbon atoms and acrylic acid or methacrylic acid,
One or more acrylic monomers excluding methyl methacrylate (hereinafter referred to as monomer (B)),
For emulsion copolymerization of 10 to 50 parts by weight and (C) 0.005 to 3 parts by weight of one or more ethylene-based polyfunctional monomers (hereinafter referred to as monomer (C)), Monomer (A), monomer (B), and monomer (C) are supplied to the polymerization system while changing their compositions continuously. and monomer (B) and monomer
(C) at the same time, and the proportion of monomer (A) in the total monomers at the start of supply is 8 to 35% by weight, and monomer (B) and monomer (C ) of monomer (B) and monomer (C) by continuously reducing the amount added per unit time as the supply time elapses so that the amount added becomes zero at the end of the supply. A method for producing an acrylic copolymer, characterized in that the supply is carried out within the supply period of the monomer (A).