JP2002513048A - Polymerization and copolymerization of ethylene - Google Patents

Abstract

  (57) [Summary] A method for polymerizing ethylene or copolymerizing ethylene and a vinyl unsaturated-containing comonomer under conditions of a temperature of 110 to 350 ° C. and a pressure of 1000 to 4000 bar in the presence of a peroxide polymerization initiator. The decomposition rate of the peroxide polymerization initiator by adding at least one non-polymerizable carboxylic acid to the polymerization mixture in an amount of 0.01 to 2.0% by mass based on the total amount of ethylene in the polymerization mixture. A method characterized by changing

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001] The present invention relates to a method for producing a polymer composition, comprising:
The present invention relates to a method for polymerizing ethylene or copolymerizing ethylene with a comonomer containing vinylic unsaturation under conditions of pressure of up to 4000 bar.

[0002] The invention further relates to the use of non-polymerizable carboxylic acids in such a method.

[0003] Methods for polymerizing ethylene alone or in the presence of other monomers containing vinylic unsaturation have been known for some time and are widely used industrially. To initiate polymerization in this manner, it is common to use a free radical initiator (eg, oxygen) or an initiator that decomposes into free radicals under the reaction conditions. The latter compounds include, in particular, organic peroxides. This type of method is, for example, U
These are disclosed in S-A 3917577 and DE-A 196 47 564.

With respect to these polymerization methods, it is effective to start polymerization at a relatively low temperature and then slowly raise the temperature. This procedure results in high conversion and high polymer density. Therefore, at the start, a polymerization initiator that decomposes into free radicals even at a low temperature is required. However, the potential of such initiators, which are generally organic peroxides, is quite dangerous and their storage requires complex precautionary measures.

[0005] Accordingly, it is an object of the present invention to use the above-mentioned peroxides that decompose at low temperatures,
It consists in initiating the polymerization effectively and controllably.

[0006] The above-mentioned object is carried out in the presence of a peroxide polymerization initiator at a temperature of 110 to 350 ° C, 100
A method for polymerizing ethylene or copolymerizing ethylene and a comonomer containing vinylic unsaturation under a pressure of 0 to 4000 bar, wherein the amount is 0.01 to 2. This invention achieves that a method characterized by changing the decomposition rate of a peroxide polymerization initiator by adding at least one non-polymerizable carboxylic acid to the polymerization mixture in an amount of 0% by mass. The inventors have found.

Further, the present inventors have found a method of using a non-polymerizable carboxylic acid to change the decomposition rate of a peroxide polymerization initiator in such a polymerization method.

By the process of the present invention, both ethylene homopolymers and copolymers of ethylene with various vinylic unsaturation-containing comonomers can be prepared.

In one embodiment of the process of the present invention, ethylene is copolymerized with an α, β-unsaturated carboxylic acid or a derivative of such a carboxylic acid.

The α, β-unsaturated carboxylic acids that can be used as comonomers in the process of the present invention are
Generally, it is a short chain carboxylic acid having 3 to 8 carbon atoms. Examples include acrylic acid, methacrylic acid, crotonic acid, maleic acid and fumaric acid, with acrylic acid and methacrylic acid forming a comonomer being particularly preferred.

In addition to the free acids, derivatives of the free acids, preferably esters of C ₂ -C ₆ alkanols, in particular ethyl, propyl, butyl, pentyl and hexyl esters, can be used as comonomers.

[0012] In another preferred embodiment of the above method, ethylene is copolymerized with vinyl acetate.

The polymerization and copolymerization process of the present invention is carried out at a temperature of 140 to 320 ° C., preferably 160 to 320 ° C.
It is preferably carried out at a temperature of 300 ° C. and is sensitive to a common comonomer.
), Especially the copolymerization of the carboxylic acid esters, preferably takes place at temperatures below 220 ° C.

The preferred pressure for carrying out the process according to the invention is in the range from 1500 to 3500 bar, in particular in the range from 2000 to 3000 bar.

The method of the present invention can be performed in various reactors known to those skilled in the art. An example is the treatment in an autoclave with a stirrer as is advantageously used, in particular for producing copolymers having a high vinyl ester content.

However, in general, treatments in which the polymerization is carried out in a tubular reactor are preferred.

Since the tubular reactor means a tubular polymerization vessel, the length-to-diameter ratio of the pressure-resistant tube is generally in the range of 10,000 to 60,000: 1. Details on the high pressure polymerization of ethylene in which tubular reactors are used are described, for example, in Ullmanns Encyklopaedie der t
echnischen Chemie, 1980, 4th edition, Volume 19, pp. 167-178, Verlag Chemie GmbH,
See D-6940 Weinheim, Germany.

In this context, all reactors of known type can be used: for example, reactors with or without the addition of cooling gas, reactors with cold pressurized water, and the like.

In the method of the present invention, polymerization is initiated using a peroxide polymerization initiator. Particularly suitable peroxides in this regard are those which decompose into free radicals only at relatively high temperatures. The decomposition temperature is the temperature at which 50% of the peroxide molecules decompose in one minute.

A suitable example of the peroxide polymerization initiator is 1,1-bis (tert-butylperoxy)
Cyclohexane, 1,1-bis (tert-butylperoxy) butane, tert-butyl peroxy-3,5,5-trimethylhexanoate, tert-butyl peroxybenzoate, 2,5-bis (tert-butylperoxy) -2 , 5-
Dimethylhexane, tert-butylcumyl peroxide, di-tert-butyl peroxide and 2,5-bis (tert-butylperoxy) -2,5-dimethyl-3-hexyne; use di-tert-butyl peroxide Is particularly preferred.

A preferred embodiment of the method of the present invention includes the use of a peroxide polymerization initiator having a decomposition temperature of 150 ° C. or higher. In this method, even if individual peroxides are used,
Mixtures of different types of peroxides may be used.

Depending on the concentration of non-polymerizable carboxylic acid added to affect the rate of decomposition, peroxides with very high decomposition temperatures may be used. This oxide is not normally used in such polymerization processes; examples include hydrogen peroxide.

Non-polymerizable carboxylic acids that can affect the rate of decomposition of the peroxide initiator include various aliphatic and aromatic carboxylic acids. Short-chain aliphatic carboxylic acids are preferred, and especially C ₁ -C ₄ alkane carboxylic acids have been found to be suitable for controlling the rate of peroxide decomposition in the polymerization. It is particularly effective to use acetic acid.

In addition, in order to keep the peroxide initiator from entraining the discharged product, a method in which a carboxylic acid which is not gaseous at maximum reaction temperature and atmospheric pressure is added to the polymerization mixture at the end of the tubular reactor. , Was found to be suitable. Examples of such acids include erucic acid or oleic acid. This decomposes the excess peroxide and enhances the quality of the polymerization product.

The amount or concentration of non-polymerizable carboxylic acid used depends on the nature of the peroxide used and on the decomposition temperature and on the activity of the desired initiator. It must therefore be adapted to the specific polymerization conditions. Generally, an amount of 0.05 to 1.0% by weight, especially 0.08 to 0.8% by weight, based on the total amount of ethylene in the polymerization mixture is suitable.

In order to make the course of the polymerization uniform, it is particularly effective for the polymerization in a tubular reactor to utilize a method in which a non-polymerizable carboxylic acid is added to the polymerization mixture from two or more different points in the reactor. Was found. Methods for injecting carboxylic acids into high pressure reactors are known to those skilled in the art.

In addition to the components described above, the polymerization mixture may further comprise conventional additives such as, for example, molecular weight regulators. The melt index of the obtained ethylene copolymer can be adjusted by such an adjusting agent. Examples of suitable regulators are hydrogen, ketones, aldehydes, alcohols, ethers, and straight-chain and branched hydrocarbons. Preference is given to using propane, propylene, methyl ethyl ketone or propionaldehyde. This regulator is generally used in an amount of 0.2 to 5 mol%, based on the ethylene to be polymerized.

The use of non-polymerizable carboxylic acids to alter the rate of decomposition of the peroxide polymerization initiator in the polymerization method of the present invention has various advantages: use of highly explosive peroxides Is avoided, the activity of the initiator can be easily adjusted by adding the carboxylic acid, and there is no need to use a complex peroxide mixture. In this way, the number of organic peroxides that need to be kept in storage can be reduced.

[0029]

【Example】

The following examples illustrate the invention in detail: [Comparative Example C1] (not according to the invention) In a tubular reactor with a tube inner diameter of 15 mm and a length of 200 m, pressure 2800 bar, inlet temperature 180 ° C., ethylene The polymerization was carried out under the conditions of a processing capacity of 1.4 t per hour. A peroxide having a low decomposition temperature (TBPIN = peroxy-3,5,5-
Tert-butyl trimethylhexanoate, decomposition temperature 160 ° C) and peroxide with high decomposition temperature (DTBP = di-tert-butyl peroxide, decomposition temperature 190 ° C)
Was used to initiate the polymerization. Propene (2.7% by weight) was used as molecular weight regulator. Table 1 shows the maximum polymerization temperature and the physical properties of the product.

Example 1 Ethylene was polymerized under the conditions of Example C1, but without TBPIN, in the presence of 0.1% by weight acetic acid. Table 1 shows the results.

Example 2 Ethylene was polymerized under the conditions of Example 1 but in the presence of 0.5% by weight acetic acid. Table 1 shows the results.

TABLE 1 Peroxide initiated polymerization of ethylene in the presence of acetic acid

[0033]

[Table 1] Result: Polymerization was possible under the same operating conditions using TBPIN or a mixture of acetic acid / DTBP.

The conversion and the physical properties of the product obtained were not substantially affected by the type of starting.

[Procedural Amendment] Submission of translation of Article 34 Amendment of the Patent Cooperation Treaty

[Submission date] January 15, 2000 (2000.1.15)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor: Dekas, Andreas Germany, D-55234, Fromborn, Schulstraße, 11 (72) Inventor: Bubak, Michael Germany, D-37120, Bofenden, Alte, Dorfstrasse, 57 A (72) Inventor Vitkowski, Lars Germany, D-37077, Göttingen, Gin Starweg, 1F term (reference) 4J011 AB02 AB04 4J015 BA05 BA07 4J100 AA02P AG04Q AJ01Q AJ02Q AJ08Q CA01 CA04 FA02 FA03 FA28 FA29

Claims (11)

[Claims] A temperature of 110 to 350 ° C. in the presence of a peroxide polymerization initiator.
A method for polymerizing ethylene or copolymerizing ethylene and a comonomer containing vinylic unsaturation under conditions of a pressure of 000 to 4000 bar, wherein the amount is 0.01 to 2. A method comprising changing the decomposition rate of a peroxide polymerization initiator by adding at least one non-polymerizable carboxylic acid to the polymerization mixture in an amount of 0% by mass. 2. The method of claim 1, wherein the at least one non-polymerizable carboxylic acid is present in an amount of from 0.05 to 1.0.
2. The method according to claim 1, wherein the amount is added to the polymerization mixture in an amount of% by weight. 3. The method according to claim 1, wherein a peroxide polymerization initiator having a decomposition temperature of 150 ° C. or higher is used. 4. The method according to claim ₁ , wherein a C ₁ -C ₄ alkane carboxylic acid is used as the non-polymerizable carboxylic acid. 5. The process according to claim 1, wherein the polymerization is carried out in a tubular reactor. 6. The process according to claim 5, wherein the non-polymerizable carboxylic acid is introduced into the polymerization mixture from two or more different points of the tubular reactor. 7. The process according to claim 5, wherein the carboxylic acid which is not gaseous at atmospheric pressure at the maximum reaction temperature is added to the polymerization mixture at the end of the tubular reactor. 8. The process according to claim 1, for homopolymerizing ethylene. 9. The process as claimed in claim 1, for copolymerizing ethylene with an α, β-unsaturated carboxylic acid or a derivative of such a carboxylic acid. 10. A process according to claim 1, for copolymerizing ethylene with vinyl acetate.
8. The method according to any one of 7. 11. Use of a non-polymerizable carboxylic acid for changing the decomposition rate of a peroxide polymerization initiator in the polymerization method according to any one of claims 1 to 10.