JPH0517244B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a modified ethylene copolymer having metal ionic crosslinks from an ethylene-ethyl acrylate copolymer.

More specifically, it is characterized by reacting an ethylene-ethyl acrylate copolymer in the presence of water and metal ions in an inert atmosphere at a temperature of 200 to 500°C and a pressure of 5 to 500 kg/ ^cm2. This invention relates to a method for producing a modified ethylene copolymer.

Conventionally, many methods for producing ethylene copolymers crosslinked with metal ions are known.

For example, as seen in Japanese Patent Publication No. 39-6810, ions have been cross-linked by reacting a water-soluble ionic metal compound with a copolymer of ethylene-α,β-ethylenically unsaturated carboxylic acid. There is a method to obtain a polyester copolymer.

In the above method, not only is there a problem that the carboxylic acid is highly corrosive to the metal during the production of the ethylene-carboxylic acid copolymer, but also the carboxylic acid in the copolymer and the metal must be reacted because the neutralization reaction is carried out using rolls. There are problems such as the possibility that the reaction with the salt may lack uniformity.

In addition, as an improved version of the above method,
There is a publication number 31556. The method uses ethylene and α, β
- A copolymer consisting of an ethylenically unsaturated carboxylic acid ester is subjected to a saponification reaction with a basic metal compound in an aliphatic alcohol or an organic solvent containing an aliphatic alcohol, and the saponification reaction product is treated with an acid. However, not only do they require complicated steps such as the use of organic solvents and acid treatment, but both of these methods yield only ionic crosslinked products with high molecular weight.

Furthermore, in Japanese Patent Publication No. 52-23673, ethylene and isopropyl (meth)acrylate, (meth)
α, β- selected from tertiary butyl acrylate
Melting a copolymer with an ethylenically unsaturated carboxylic acid ester and a metal compound such as an acetate, a formate, or an oxide of a metal having a valence of 1 to 3 in the -A group of the periodic table. Mix and temperature 200-320℃
A method for producing an ionically crosslinked ethylene copolymer in a one-step process under the following conditions is disclosed.

However, even in this method, it is an essential condition that the copolymer used as the copolymer base is resistant to thermal cleavage reactions of polymer chains, and the metal compound used must also be resistant to thermal cleavage reactions of polymer chains. The purpose of this method is to produce a high molecular weight ionically crosslinked ethylene copolymer, since it must not participate in or suppress the reaction.

On the other hand, recently, low molecular weight ethylene copolymers having ionic crosslinking have been in demand in various fields such as emulsion adhesives, raw materials for water-based paints, hot melt adhesives, and resin modifiers.

As a result of intensive research in view of the above points, the present inventors have found that a modified ethylene copolymer having a desired amount of metal ionic crosslinks, which has been arbitrarily reduced in molecular weight from an ethylene-ethyl acrylate copolymer, can be produced in a one-step process. So, we found a way to directly manufacture it.

The first object of the present invention is to provide a method for producing a modified ethylene copolymer having metal ion crosslinks, which is arbitrarily reduced in molecular weight from a relatively high molecular weight ethylene-ethyl acrylate copolymer.

A second object of the present invention is to provide a method for producing a modified ethylene copolymer having a desired amount of metal ionic crosslinks.

A third object of the present invention is to provide a method for producing a modified ethylene copolymer with good hue.

Furthermore, the fourth object of the present invention is to prepare a modified ethylene copolymer having metal ion crosslinks of an ethylene-acrylic acid binary copolymer substantially free of unsaponified ethyl acrylate or an arbitrary amount of ethyl acrylate. An object of the present invention is to provide a method for producing a modified ethylene copolymer having metal ion crosslinking of the remaining ethylene-ethyl acrylate-acrylic acid terpolymer. The present invention has been made to achieve the above object.

That is, according to the present invention, a relatively high molecular weight ethylene-ethyl acrylate copolymer is heated in an inert atmosphere in the presence of water and metal ions at a temperature of 200 to 200°C.
The above-described modified ethylene copolymer can be produced by reacting at 500° C. and a pressure of 5 to 500 kg/cm ² .

The ethylene-ethyl acrylate copolymer referred to in the present invention refers to a commercially available ethylene-ethyl acrylate copolymer having a relatively high molecular weight that can be easily obtained by, for example, a high-pressure copolymerization method known in the industry using a free radical catalyst. The copolymer has a melt index of about 300 g/10 min or less and a content of ethyl acrylate in the molecular chain of about 1 to 40% by weight, preferably 5 to 30% by weight. In addition, the method of creating an inert atmosphere in the present invention is not particularly limited, but for example, a method of completely eliminating air by passing an inert gas such as nitrogen, carbon dioxide, argon, or helium through the reaction system is possible. It is preferred to use nitrogen.

Furthermore, the reaction temperature and reaction pressure when carrying out the present invention depend on the properties of the raw materials used, namely ethylene-
Although it is controlled by factors such as the average molecular weight of the ethyl acrylate copolymer, the content of ethyl acrylate, the degree of molecular weight reduction, and the amount of coexisting water, the reaction temperature is 200 to 500 °C, and the reaction pressure is 5 to 5. 500Kg/cm ² and reaction time is 1 to 10 hours, preferably 2 to 6 hours.
It is a range of time.

If the reaction temperature is less than 200°C, it is difficult to lower the molecular weight, and if the temperature exceeds 500°C, ethyl acrylate in the copolymer will volatilize and decarboxylation reactions will occur, resulting in severe decomposition, which is preferable. do not have.

The metal ions added in the present invention are 1
It is best to add in the form of an aqueous solution of a metal compound having ~3 valences, and the first ion group is
Na ⁺ , K ⁺ , Li ⁺ , Mg, Ca, Ba,
The ions are selected from Zn, Sb, Cu, Fe, Al, Fe and mixtures thereof, and among these, alkali metal ions are particularly preferred, and among the metal compounds forming the second ion group source, so-called Sodium hydroxide, magnesium hydroxide, potassium hydroxide, zinc hydroxide, calcium oxide, sodium methoxide, sodium ethoxide, magnesium oxide, nickel acetate, sodium carbonate as basic metal compounds,
Magnesium acetate, zinc acetate, etc. are included.

In order to achieve the above-mentioned purpose of producing a modified ethylene copolymer having an arbitrarily low molecular weight in the method of the present invention, it is necessary to produce a modified ethylene copolymer having a relatively high molecular weight.
Temperature in the presence of water and metal ions in an inert atmosphere using ethyl acrylate copolymer as raw material.
It is important to carry out the reaction under conditions of 200 to 500° C. and a pressure of 5 to 500 kg/cm ² , and among these reaction conditions, the most important factors include the presence of water and temperature conditions. Note that water in the present invention includes liquid, water vapor, and a mixture thereof.

The molecular weight of the ethylene-ethyl acrylate copolymer can be arbitrarily lowered by adjusting the above temperature conditions and especially the amount of water. At the same time, the ethylene-acrylate copolymer does not contain substantially unsaponified ethyl acrylate. It is possible to produce a modified acid binary copolymer or a modified ethylene-ethyl acrylate-acrylic acid ternary copolymer in which any amount of ethyl acrylate remains. For example, in the production of a modified ethylene-acrylic acid binary copolymer substantially free of unsaponified ethyl acrylate, the amount of water is This is achieved by carrying out the reaction under conditions of 400 mol or more, preferably 400 to 1,500 mol.

However, since it is desirable that the amount of water added is as small as possible from the viewpoint of energy consumption cost, it is appropriately selected in consideration of the required physical properties and intended use.

The molecular weight of the above-mentioned low molecular weight modified ethylene copolymer having ionic crosslinking varies depending on various uses, but is generally a viscosity average molecular weight of 30,000 or less, preferably 15,000 or less.

The viscosity average molecular weight of the present invention was determined by measuring the intrinsic viscosity [η] in a decalin solvent at 135°C and using the following formula.

[η]=KM〓 (K=14.3×10 ^-5 (dl/g), α=0.82) Another object of the present invention is to provide a method for producing a modified ethylene copolymer having a desired amount of metal ionic crosslinks. However, the amount of the metal ion added depends on the reaction temperature, reaction pressure, reaction time, amount of water added, content of ethyl acrylate in the raw materials, degree of lowering of the molecular weight of the ethylene-ethyl acrylate copolymer, In a range of 5 to 80 mol%, preferably 10 to 70 mol%, based on the ethyl acrylate in the ethylene-ethyl acrylate copolymer, while considering the influence of various factors such as the type and concentration of metal ions. Ionic crosslinking is desirable to obtain solid state properties and excellent properties in the molten state.

Furthermore, the present invention aims to provide a method for producing a modified ethylene copolymer with a good hue, but in order to obtain the modified ethylene copolymer with a good hue, the oxygen concentration in the reaction system must be adjusted to a normal level. The value measured by Brady method is 5ppm or less, preferably
It is produced by carrying out the reaction at a concentration of 3 ppm or less, particularly preferably 1 ppm or less.

The following method can be used to reduce the oxygen concentration in the reaction system to 5 ppm or less.

First, in order to eliminate oxygen dissolved in the water in the reaction system, inert gas is bubbled from the bottom of the reaction vessel to completely eliminate dissolved oxygen, and the air inside the reactor is pressurized with inert gas. This can be achieved by repeating the depressurization and purging operations.

The effects of the present invention can be obtained, for example, from a relatively high molecular weight raw material ethylene-ethyl acrylate copolymer with an average molecular weight of tens to hundreds of thousands to a low molecular weight modified ethylene with an average molecular weight of several thousand that does not substantially contain ethyl acrylate. This effect is most noticeable when the degree of molecular weight reduction is very large, such as in the production of copolymers.

As mentioned above, the method of the present invention has the following characteristics: (1) A low molecular weight ionic crosslinked ethylene copolymer can be directly produced in a one-step process; (2) A raw material ethylene-ethyl acrylate copolymer It is possible to arbitrarily control the lowering of the molecular weight and the residual amount of ethyl acrylate. (4) It is possible to provide a modified ethylene copolymer with good hue; and so on.

Modified ethylene copolymer emulsion adhesives obtained by the method of the present invention, adhesives such as hot melt adhesives, paints such as water-based paints, or as lubricants, pigments, and fillers for improving moldability. It is used as a dispersion aid and coupling agent for various polymers, asphalts, and waxes, as a modifier and plasticizer for various polymers, asphalt, and waxes, and as a compounding agent for improving the performance of engineering plastics and as a crystallization accelerator.
It is used in various fields such as cables, food, packaging, and cash registers.

Hereinafter, the present invention will be explained in more detail with reference to Examples, but it is clear that widely different embodiments can be constructed without departing from the spirit and scope of the invention, and therefore the present invention is limited in the accompanying claims. The invention is not otherwise limited to these particular implementations.

Example 1 Ethylene-ethyl acrylate polymer (ethyl acrylate content 14% by weight, melt index 9
g/10min) and 2 kg of water in which 11 g of sodium hydroxide was dissolved were placed in a pressurized container with a capacity of 3.8 and equipped with a magnetic stirrer, and nitrogen gas was bubbled from the bottom of the container for 1 hour to submerge it in the water. After completely eliminating dissolved oxygen, the air inside the pressurized container was pressurized with nitrogen gas (50Kg/cm ² ) and depressurized (1Kg/cm ² ) five times to reduce the oxygen concentration in the system. When measured (Brady method)
It was less than 1 ppm. Next, the container was heated and reacted in a nitrogen atmosphere for 4 hours at 350° C. and 200 kg/cm ² , and then cooled in air.

The product has a viscosity average molecular weight of 6000, and the infrared absorption curve shows that this compound has 1 mol% of acrylic acid and 99 mol% of sodium acrylate based on the ethyl acrylate of the ethylene-acrylic acid copolymer.
It was a compound consisting of

Moreover, the hue of this product was 1 or less on the Gardner color number.

Example 2 Ethylene-ethyl acrylate polymer (ethyl acrylate content 14% by weight, melt index 9)
g/10min) 200g of magnesium acetate dissolved in 44g of water and 2kg of water were placed in a pressurized container with a capacity of 3.8mm equipped with a magnetic stirrer, and after completely eliminating the air inside the container with nitrogen gas, The mixture was heated and reacted in a nitrogen atmosphere at 350° C. and 200 Kg/cm ² for 4 hours, and then cooled in air.

The product has a viscosity average molecular weight of 6000, and the infrared absorption curve shows that this compound contains 2 mol% of acrylic acid, 1 mol% of ethyl acrylate, and 1 mol% of acrylic acid, based on the ethyl acrylate of the ethylene-acrylic acid copolymer. It was a compound consisting of 97 mol% magnesium.

Example 3 200 g of ethylene-ethyl acrylate copolymer (ethyl acrylate content 14% by weight, melt index 9 g/10 min) was mixed with 2 kg of water in which 48 g of zinc acetate was dissolved, and the content was prepared using a magnetic stirrer.
3.8, and after completely expelling the air inside the container with nitrogen gas, it was heated and reacted in a nitrogen atmosphere for 4 hours at 350°C and 200Kg/ ^cm2. After that, it was air cooled.

The product has a viscosity average molecular weight of 6000, and the infrared absorption curve shows that this compound contains 2 mol% of acrylic acid, 1 mol% of ethyl acrylate, and zinc acrylate based on the ethyl acrylate of the ethylene-acrylic acid copolymer. It was a compound consisting of 97 mol%.

Claims (1)

[Scope of Claims] 1. Ethylene with a melt index of 300 g/10 minutes or less and an ethyl acrylate content of 1 to 40% by weight.
Ethyl acrylate copolymer in the presence of water and metal ions in an inert atmosphere at a temperature of 200-500℃,
A method for producing a modified ethylene copolymer, which comprises reacting under pressure conditions of 5 to 500 Kg/cm ² to produce a modified ethylene copolymer having a viscosity average molecular weight of 30,000 or less. 2. The method for producing a modified ethylene copolymer according to claim 1, wherein the reaction is carried out at an oxygen concentration of 5 ppm or less.