JPH01156309A - Production of ethylene copolymer - Google Patents

Abstract

PURPOSE:To obtain the title copolymer of excellent quality stably even at relatively low temperature by polymerizing ethylene, an acid anhydride monomer, and a (meth)acrylate or vinyl ester in the presence of an antioxidant. CONSTITUTION:The title copolymer is obtained by the radical polymerization of 40-99wt.% ethylene (A), 0.2-20wt.% radical-polymerizable acid anhydride monomer (B) (e.g., maleic anhydride), and 60wt.% or less (meth)acrylate or vinyl ester (C) (e.g., methyl methacrylate) containing 0.1wt.% or less hydrolyzable component present as impurity at 100-300 deg.C and 700-3,000atm in the presence of 50-1,000ppm, based on total monomers, antioxidant (D) (e.g., 2,6-di-tert- butyl-4-methylphenol) added preferably as a mixture with components B and C at a point between the outlet of a first-stage booster and a position where a recycling gas from a high-pressure separator is mixed, and a polymerization initiator (E) (e.g., di-tert-butyl peroxypivalate).

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for producing an ethylene copolymer. More specifically, ethylene, a radically polymerizable acid anhydride monomer, and (meth)acrylate or vinyl ester are heated under high pressure.
The present invention relates to a method for stably producing radical copolymerization at high temperatures.

(Prior art) High-pressure polyethylene production is carried out at relatively high temperatures in order to improve reaction stability and conversion rate during production, but in copolymerization reactions that use comonomers with large chain transfer such as water-based copolymerization reactions, The polymerization reaction at high temperatures promotes chain transfer and reduces the molecular weight of the copolymer, leading to a decline in the physical properties of the product. Furthermore, radical reactions of acid anhydrides at too high temperatures may lead to runaway reactions, which is not desirable from a safety standpoint. On the other hand, if polymerization is carried out at a low temperature in order to suppress a decrease in molecular weight, the polymerization system tends to undergo phase separation, which may reduce reaction stability or increase the power required for agitation in the reactor, so this is not preferable. do not have. Therefore, hitherto, no method has been established for stably and commercially producing an ethylene copolymer containing an acid anhydride group, such as an aqueous one, by high-pressure radical polymerization.

(Problems to be Solved by the Invention) The present invention attempts to propose a production method in which the reaction is stable even during polymerization at a relatively low temperature, and there are no problems such as an increase in the power of the stirrer.

(Means for solving the problem) In order to solve the above problem, as a result of intensive research, ethylene, a radically polymerizable acid anhydride monomer, and (meth)acrylate or vinyl ester were mixed at a pressure of 700 to 3000 atm. A method for producing an ethylene copolymer by radical polymerization under pressure at a temperature of 100 to 300°C, the method comprising adding an antioxidant to a polymerization reactor. reached. According to this method, the above copolymer can be produced even at a relatively low temperature, and a copolymer of excellent quality can be provided.

The present invention will be explained in detail below.

The radically polymerizable acid anhydride monomers referred to in the present invention include maleic anhydride, itaconic anhydride, citraconic anhydride, himic anhydride, methylhimic anhydride, and derivatives thereof. Moreover, one or more types from the above group can be selected and used.

More preferable than the above group are maleic anhydride and itaconic anhydride.

In addition, (meth)acrylates include the following general formula (I),
Examples include compounds represented by (II).

R (R is an organic group having at most 20 carbon atoms.

) More specific examples include methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, isodecyl methacrylate, lauryl methacrylate, lauryl-tridecyl methacrylate,
Tridecyl methacrylate, cetyl-stearyl methacrylate, stearyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, dimethylamine ethyl methacrylate, diethylaminoethyl methacrylate, glycidyl methacrylate, tetrahydrofurfuryl methacrylate, and methyl acrylate, acrylic acid Ethyl, propyl acrylate, isobutyl acrylate, tert-butyl acrylate, 2-ethylhexyl acrylate,
Octyl acrylate, isodecyl acrylate, lauryl acrylate, tridecyl acrylate, cetylstearyl acrylate, cyclohexyl acrylate, benzyl acrylate, dimethylaminoethyl acrylate, diethylamine ethyl acrylate, glycidyl acrylate, tetrahydrofurfuryl acrylate Preferably, R is a (meth)acrylate having at most 8 carbon atoms. Particularly preferably, R has at most 4 carbon atoms.

The vinyl ester used in the present invention is represented by the following general formula value.

CH2= CH(I[) C0R (R is an organic group having at most 8 carbon atoms.) More specific examples include vinyl acetate and vinyl propionate.

Furthermore, the antioxidant referred to in the present invention refers to a phenolic antioxidant, and monophenol-based, bisphenol-based, and polymeric phenol-based antioxidants can be used.

The antioxidants used in the present invention are nuclear-substituted phenols, biphenols, and bisphenols. In this case, each phenolic nucleus contains hydroxy, carboxyl, carginyl, nitro, amino, amino-lower alkyl, and lower alkyl. At least one substituent selected from the constituent groups of amino, lower alkyl, lower alkenyl, lower alkoxy and lower alkacyl groups is included. Such antioxidants can be used alone or in combination with one or more other antioxidants of this type.

A low alkyl group whose substituent on the phenolic nucleus is up to C4,
Particularly favorable results in the case of methyl, isopropyl and tert-butyl lower alkenyl groups in the 04 dimension, vinyl, α-methyl-substituted vinyl and allyl groups, and lower alkoxy groups in the 03''!1, especially methoxy and hydroxy groups. will occur.

In the case of bisphenols, the bases that link each phenolic nucleus may be of various types. We have found that lower alkenylene bisphenols such as methylene and ethylene bisphenol, lower alkenylene bisphenols such as ethylene and hyfurobenylene bisphenol, and thiobisphenol are particularly effective.

Good results are generally obtained when using antioxidants of the type described above which have at least two, preferably three or more substitutions on each phenolic nucleus. Therefore, compounds such as parahydroxybenzaldehyde, hydroquinone monomethyl ether, p-amine phenol are also effective, but xylenol, especially 3,5 xylenol, 2,6 diisoprobyl phenol, 2-sec-1 butylhydroxyanisol, 4 -tert-butylpyrocatechol, 2,4-bis(1,1-dimethyl-propylphenol), 4,4'thiobis-(6-tert-butyl-meta-cresol), 4,4'methylenebis(6-tert-butyl-meth-cresol), Butyl-
ortho-cresol), 4,4'-methylenebis(2,
More preferably, compounds such as 6-di-tert-butylphenol) and 2,6-di-tert-butyl-4-methylphenol are used.

In the case of the above antioxidants, 3,5-xylenol, 2,6-
It is particularly effective to use mononuclear phenols when using di-tert-butyl-4-methylphenol, 2,6-di-tert-butyl-4-ethylphenol or 2-tert-butylhydroxyanisol.

The process for producing ethylene copolymers according to the present invention is carried out in the presence of at least one free radical initiator.

The catalyst used in this radical polymerization is a compound that generates free radicals, such as oxygen, dialkyl i4-oxide such as ditertiary butyl peroxide, tertiary butylcumyl 4-oxide, diacyl peroxide, acetyl peroxide, Diacyl peroxides such as inbutyl peroxide and octanoyl peroxide, diisopropyl peroxydicarbonate,
No.1 oxydicarbonates such as di-2-ethylhexyl oxydicarbonate (di-2-ethylhexyl oxydicarbonate); Oxyesters, ketone peroxides such as methyl ethyl ketone peroxide and cyclohexanone peroxide, peroxy ketals such as 1,1-bistershyabutyl peroxycyclohexane, 2,2-bistershyabutyl peroxy, and octane, and tert-butyl hydroperoxide. , hydroperoxides such as cumene hydroperoxide, and azo compounds such as 2.2 azobisisobutyronitrile.

Ethylene and radically polymerizable acid anhydride monomer are 700-3
Polymerization is carried out at a pressure of 1,000 atm and a temperature range of 100 to 300°C, and the monomers to be subjected to polymerization are fed into the polymerization vessel through a two-step pressurization process. In particular, the first stage booster increases the pressure to at most 300 atmospheres, and the second stage
Pressurization of a given polymer head is carried out using a stage pressurizer.

ti, it is preferable that the antioxidant is pressurized by a pump to the pressure of the first stage booster and then fed before the second stage booster; It is desirable to carry out the process after the outlet and between the parts where the recycled gas from the high-pressure separator is mixed.

The antioxidant in the present invention is preferably fed to the first zone of the polymerization reactor through the pressure increasing process.

It is desirable that the antioxidant be dissolved in (meth)acrylate Δ and added together with an inert solvent-compatible acid anhydride monomer such as tsukurafins.

Using the antioxidant disclosed in the present invention and the radically polymerizable acid anhydride monomer simultaneously in the form of a solution may cause the acid anhydride and the hydroxyl group to react. Reactions with acid anhydride groups are extremely likely to occur.

Therefore, the solvent constituting the above solution must be sufficiently purified. In particular, when (meth)acrylate is used, it is essential that the (meth)acrylate does not undergo hydrolysis to generate acid components. Specifically, the amount of hydrolyzed components present as impurities must be at most 0.1% by weight.

The antioxidant, a radically polymerizable acid anhydride monomer, and (meth)
Feeding the acrylate or vinyl ester as a solution prevents thermal polymerization of the radically polymerizable acid anhydride monomer and (meth)acrylate or vinyl ester during storage in a tank or feeding into a polymerization reactor. It is also meaningful for the purpose of

one! Furthermore, it is important to feed the antioxidant mainly to the first zone of the polymerization reactor in order to solve instability of polymerization caused by fouling in the polymerization reactor throughout the reactor.

In particular, feeding the antioxidant between the outlet of the first-stage pressure booster and the recycle gas mixing section from the low-pressure separator can bring about effective mixing of the antioxidant between the polymerized monomers. It is extremely meaningful.

The antioxidant used in the present invention has an amount of 50 to 11,000 pp, preferably 80 to 5,001) m, more preferably 10
Add 0 to 200 ppm. If the amount added is less than 50 ppm, the expected effect will not be achieved.
If it exceeds pp, a large amount of polymerization initiator will be required due to the radical capture of the antioxidant, and favorable results will not be obtained.

The ethylene copolymer produced in the present invention has an ethylene content of 40 to 99% by weight, a radically polymerizable acid anhydride monomer of 0.2 to 20% by weight, and a (meth)acrylate or vinyl ester content of at most 60% by weight. % by weight.

More preferably, the ethylene content is 50 to 95% by weight.
, 1.0 to 15% by weight of a radically polymerizable acid anhydride monomer, and 3% of (meth)acrylate or vinyl ester.
and 49% by weight.

Particularly preferably an ethylene content of 60 to 90% by weight
, 2.0 to 10% by weight of a radically polymerizable acid anhydride,
and (meth)acrylate from 5 to 38% by weight.

(Example) In the following Examples and Comparative Examples, an autoclave type reactor having a volume of 4 and divided into two zones was used.

Example 1 The monomer composition at the reactor inlet was (4) ethylene 97,
58% (weight% and below are the same), (B) methyl methacrylate 2.0%, (C) maleic anhydride 0.40%, (
c) 2.6-ditertiarybutyl-4-methylphenol (B) (C) (D) so that the concentration is 200 ppm.
The mixed solution was injected upstream of the second stage compressor and fed into the first zone of the reactor after compression together with ethylene gas. A radical copolymerization reaction is carried out in a reactor using ditertiary butyl peroxyvivalate as an initiator, and a high-pressure separator,
A polymer product was obtained by separating the produced polymer and unreacted monomer using a low pressure separator. Polymerization at a temperature of 190-205℃
The reaction was carried out at a pressure of 1950 atm, and the reaction was sufficiently stable and could be operated for a long time without any particular problem. Although the obtained polymer contains a very small amount of component (D), it is essentially a terpolymer of (B) (0), determined using an infrared absorption spectrum and a 13c-NMR spectrum. The composition was 87.8% ethylene and 9.8% methyl methacrylate.
2%.

The maleic anhydride content was 3.0%. The MI of the polymer is 4
．． 5 (9,710 minutes) and had excellent adhesiveness and moldability, so it could be used as various laminate products.

Examples 2 to 5 Types and compositions of (B) and (C) components in Example 1, 2
, 6-ditertiarybutyl-4-methylphenol was varied in the same manner as in Example 1.

The results are shown in Table 1. In all cases, the reaction stability was good and continuous operation for a long time was possible, and the resulting polymer had good physical properties and could be used for various purposes.

Comparative Example 1 Polymerization was carried out under the same conditions as in Example 1 except that 2.6-ditertiarybutyl-4-methylphenol was not used. In this case, (although the cause is not clear) there is an increase in the required stirring power over time, which is presumed to be due to phase separation in the reactor and adhesion of polymers, and temperature hunting increases, making it difficult to control the temperature to a specified level. When this became difficult, stable operation for long periods of time was impossible.

To avoid this situation, the polymerization temperature is increased to 260-280°C (the initiator is ditertiary butyl 4-
(The mixture was changed to a mixture of oxide and tert-butyl peroxy-2-ethylhexanoate) Although the reaction stability was restored, the MI of the produced polymer was about 2,000. This polymer is difficult to mold, and has weak adhesive strength due to the effects of low molecular weight materials, making it impossible to put it to practical use.

Comparative Example 2 Under the conditions of Example 10, 2,6-ditertiarybutyl-4-
Polymerization was carried out with the feed amount of methylphenol being 1200 ppm. In this case, due to the large amount of antioxidant, a large amount of initiator was required to maintain the polymerization temperature.

Since the capacity of the initiator supply pump was limited, we tried to increase the concentration of the initiator (the initiator is used as a solution of iso-1? rough-in), but this made it difficult to uniformly disperse the initiator and Since a so-called hot spot occurred and signs of an ethylene decomposition reaction were observed, the polymerization had to be stopped immediately.

(Effects) According to the production method of the present invention, it is possible to stably and efficiently produce ethylene, a radically polymerizable acid anhydride monomer, and a (meth)acrylate terpolymer, and the adhesive properties can be improved. A good ethylene copolymer material can be provided.

Claims (4)

[Claims] (1) Ethylene and radically polymerizable acid anhydride monomer, (
meth)acrylate or vinyl ester from 700 to 3
A method for producing an ethylene copolymer by radical polymerization at a temperature of 100 to 300°C under a pressure of 0,000 atmospheres, characterized in that an antioxidant is added to the polymerization reactor. manufacturing method. (2) Ethylene according to claim 1, characterized in that the antioxidant is added after the outlet of the first stage booster and before the recycled gas mixing site from the high pressure separator. Method for producing a copolymer. (3) The method for producing an ethylene copolymer according to claim 1, characterized in that an antioxidant is added to the first zone of the polymerization reactor. (4) A patent claim characterized in that when adding an antioxidant, the antioxidant, a radically polymerizable acid anhydride monomer, and (meth)acrylate or vinyl ester are mixed and added as a solution. A method for producing an ethylene copolymer according to item 1.