JPS598297B2 - Polyolefin dispersion and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a polyolefin dispersion having excellent properties and a method for producing the same.

Aqueous polyolefin dispersions are increasingly being used for adhesion and coating of paper, textiles, wood boards, metals, etc.

Polyolefins are originally nonpolar and are not compatible with water, so in order to obtain an aqueous polyolefin dispersion, a method is generally used in which polyolefins are modified to give them polarity and an emulsifier is used. It is known that when a coating film is formed from such an aqueous dispersion, the emulsifier remains in the coating film, impairing the physical properties of the coating film. However, it is generally difficult to obtain a stable dispersion unless an emulsifier is used. On the other hand, as a method for imparting polarity to polyolefins, a method has been used in which carboxyl groups are incorporated into polyolefins, and in the production of aqueous dispersions, alkali metal salts have been used instead. When such an alkali metal salt of a carboxyl group-containing polyolefin is contained in a coating film, water resistance, which is a major characteristic of polyolefin, is often impaired. In the present invention,
The object of the present invention is to provide a novel polio-fin aqueous dispersion suitable for paints that do not particularly require the inclusion of emulsifiers and alkali metal salts such as those mentioned above, and a method for producing the same.

Another object of the present invention is to provide a stable aqueous polyolefin dispersion that exhibits a suitable viscosity as a coating material, and a method for producing the same. That is, the present invention provides polyolefins of 50 to 9
5 parts by weight and a polyvalent metal salt of carboxyl group-containing polyolefin wax having an acid value of 30 to 150 5 to 50
parts by weight, and the amount of polyvalent metal present as the salt is 0.
The present invention is an aqueous dispersion of a polyolefin composition having a particle size of 0.5 to 100 microns with a composition of 0.01 to 1.0 meq/g composition.

The present invention also provides a polyolefin composition comprising 50 to 95 parts by weight of a polyolefin and 5 to 50 parts by weight of an alkali metal salt of a carboxyl group-containing polyolefin wax having an acid value of 30 to 150, with a particle size of 0.5 to 100.
In this method, an aqueous dispersion of μ is brought into contact with a water-soluble polyvalent metal salt to produce the aqueous dispersion. In general, alkali metal salts are considered to be stable in aqueous dispersions of carboxylic acid-modified polyolefins, and polyvalent metal salts such as calcium and zinc are not preferred because they impair the stability of the dispersion (e.g. Special Publication No. 45-29909, Special Publication No. 33302-1972, Special Publication No. 42620-1974, etc.). However, in aqueous dispersions such as those of the present invention, in systems containing only alkali metal salts, particles tend to float and the dispersion tends to break down during long-term storage, whereas in systems containing polyvalent metal salts, the dispersion is extremely stable. It is surprising that The dispersion of the present invention is an aqueous dispersion of a composition of a polyolefin and a polyvalent metal salt of a carboxyl group-containing polyolefin wax.

Here, polyolefins include ethylene, propylene, 1-
It is a homopolymer or a copolymer of 1-olefinic unsaturated hydrocarbons such as butene and 4-methyl-1-benzene.

For example, polyethylene, polypropylene, poly-1-butene, poly-4-methyl-1-benzene, ethylene/propylene copolymer, ethylene/1-butene copolymer, propylene/1-1-butene copolymer, ethylene/vinyl acetate copolymer, etc. polymers, ethylene/acrylic acid ester copolymers, etc. Carboxyl group-containing polyolefin waxes are wax-like polyolefins containing COOH groups and/or acid anhydride groups, and have a structure in which 1-olefins and unsaturated carboxylic acids or their anhydrides are randomly copolymerized, or It has a structure in which an unsaturated carboxylic acid or its anhydride is grafted onto a polyolefin wax.

Examples of the unsaturated carboxylic acid or anhydride thereof include acrylic acid, methacrylic acid, maleic acid, fumaric acid, citraconic acid, itaconic acid, 5-norbornene-2,3-dicarboxylic acid, and anhydrides thereof. For the stability of the aqueous dispersion, it is preferable to use a polyolefin with a larger molecular weight than the carboxyl group-containing polyolefin wax used. For example, the intrinsic viscosity [η] measured in decalin at 135°C is at least 0.2 or more. Preferably away.

As a carboxyl group-containing polyolefin wax,
η] is preferably from 0.05 to 0.8, and its acid value should be from 30 to 1501, preferably from 50 to 120. The acid value here is the number of potassium hydroxide required to neutralize 1 g of sample. If a material with a low acid value is used, a stable dispersion will not be obtained. Furthermore, if a material with too high [η] is used, it will be difficult to obtain a stable aqueous dispersion. On the other hand, the [η] of polyolefin is 0.1 to 5.0.
In particular, it is preferably in the range of 0.5 to 3.0. Polyvalent metal salts for carboxyl group-containing polyolefin waxes include, for example, magnesium salts, calcium salts, strontium salts, barium salts, zinc salts, cadmium salts, cupric salts, ferrous salts, ferric salts, aluminum salts, etc. can be mentioned.

It is not necessary that all of the carboxyl groups of these be converted into these salts, and a portion may remain in the form of a free acid or anhydride or a monovalent metal salt. However, in a composition comprising a polyolefin and a carboxyl group-containing polyolefin wax polyvalent metal salt, the amount of the polyvalent metal present as the salt is 0.01 to 1.0 milliequivalent/g composition, particularly preferably 0.05 to 0. .5 milliequivalent/g
A range of compositions is necessary to maintain the appropriate viscosity required for the coating and to keep the dispersion stable over long periods of time. The particle diameter of the two components in the aqueous dispersion is 0.5 to 100μ, preferably 1 to 10μ.
, which is slightly larger than that of conventional dispersions.

If the particle size is too small, the particles tend to coagulate together, which impairs stability, and if the particle size is too large, a stable dispersion cannot be obtained. The particle shape is preferably substantially spherical, and the particle size distribution is preferably as narrow as possible.
Such aqueous dispersions usually contain up to 80% by weight of said particles and their viscosities generally range from 100 to 5000 centiboas, preferably from 500 to 2000 centiboas.

The aqueous polyolefin dispersion of the present invention can be preferably produced by the following two methods.

That is, a polyolefin composition comprising 50 to 95 parts by weight of a polyolefin and 5 to 50 parts by weight of an alkali metal salt of a carboxyl group-containing polyolefin wax having an acid value of 30 to 150 has a particle size of 0.5 to 10.
A 0μ aqueous dispersion is prepared in advance, and water-soluble polyvalent metal salts such as chlorides, sulfates, and nitrates, specifically magnesium chloride, calcium chloride, barium chloride,
A strong acid salt such as zinc chloride, zinc sulfate, cupric chloride, cupric sulfate, cupric nitrate, ferrous chloride, ferric chloride, or aluminum chloride may be added to cause the two to react. The aqueous dispersion is a mixture of 50 to 95 parts by weight of a polyolefin and 5 to 50 parts by weight of a carboxyl group-containing polyolefin wax having an acid value of 30 to 150, in a molten state, and a basic alkali metal compound such as sodium hydroxide or potassium hydroxide. It can be obtained by dissolving the polyolefin and pouring it into water maintained at a temperature higher than the melting point of the polyolefin.

The details of this technology are disclosed in the earlier application filed by the same applicant, dated July 22, 1975. The reaction temperature between this aqueous dispersion and the water-soluble polyvalent metal salt is arbitrary.
For example, mixing is carried out at a temperature of 0 to 100° C. for about 1 second to 1 hour. There is no particular need to use an excessive amount of the water-soluble polyvalent metal salt, and a theoretical amount is sufficient. The progress of the reaction can be determined by the increase in the viscosity of the dispersion. In this method, the raw material aqueous dispersion is stable only at a relatively low concentration, and its storage period is not very long, whereas the aqueous dispersion of the present invention is stable even at a high concentration. It can withstand long-term storage for several months. The second method for producing the aqueous dispersion of the present invention is a method in which a water-soluble polyvalent metal salt is allowed to coexist with the basic alkali metal compound when producing the raw material aqueous dispersion of the first method, According to this method, it is possible to produce a desired aqueous dispersion in one step.

That is, for example, polyolefin and carboxyl group-containing polyolefin wax are mixed and melted, and water in which a basic alkali metal compound such as sodium hydroxide or potassium hydroxide and a water-soluble polyvalent metal salt as mentioned above is dissolved is heated to a temperature higher than the melting point of the polyolefin. This is a method in which the temperature is preferably kept at a temperature 30° C. or more higher than the melting point and 300° C. or lower, and the mixture is charged while stirring vigorously. The basic alkali metal compound should be used in an amount equal to or more than the desired polyvalent metal salt. is necessary. The amount of the polyvalent metal salt used is preferably approximately equal to the theoretical amount, or in some cases slightly in excess. The amount of water used is determined by the desired concentration of the aqueous dispersion. A pigment, a plasticizer, a thickener, etc. may be further added to the aqueous dispersion of the present invention as required.

The aqueous dispersion of the present invention is stable over a long period of time and has an appropriate viscosity, so it is suitable for use in paints, and it is possible to form a coating film with excellent adhesion and water resistance. Example 1, Comparative Example 1 7.7 kg of maleic anhydride grafted polyethylene wax ([η] = 0.2) with an acid value of 50 and polyethylene with a density of 0.927 (decalin method, [η] = 0.7, melting point 12
0°C) 30.7k9 was melt-mixed at 200°C.

Put 165 g of water 6011 potassium hydroxide into a pressure-resistant homomixer with an internal volume of 1201, heat it to 180 ° C.
The molten mixture was pumped for 4 hours while stirring at 0 rpm. After further stirring for 30 minutes, the resulting aqueous dispersion was cooled to room temperature, with a concentration of 640 g/11 and a viscosity of 11 cps (
(25℃), the particles are spherical and the average particle size is 2.0μ
It was hot. Add this slurry and 1.28% by weight of the metal salts listed in Table 1 based on the polymer particles, and mix with a homomixer for 1000 rpm.
m1 Stirred at room temperature for 10 minutes. The results are shown in Table 1. Reference example 1 Polyethylene 28 with density 0.918, [η] = 0.49
kg and 14 kg of maleic anhydride grafted polyethylene wax having an acid value of 50 were melt-mixed at 170°C.

450 g of water 6011K0H and 249.5 g of CaC' in a pressure-resistant container with an internal volume of 1001 equipped with a turbine type stirrer.
was heated to 180 °C, and the molten mixture was charged with a gear pump for 4 hours while stirring at 500 rpm. After further stirring for 30 minutes, the resulting aqueous dispersion was slowly cooled to room temperature, with a concentration of 700 g/l and a viscosity of 900 cps (At25°
), and the particles were spherical and had an average particle size of 1.5μ. Add 3 parts of water to the polyolefin dispersion 601 obtained here.
g and Red Garla (Toda Kogyo 120M1 average particle size 0.1
7μ) 0.42g into a container equipped with a turbine type stirrer 3
Stir at 00 rpm (room temperature) for 30 minutes. This dispersion had a viscosity of 300 cps (at 25°C) and 15 seconds in a food cup. This dispersion was sprayed onto an aluminum plate (100 μm thick) at an air pressure of 3 kg/d using a commercially available paint spray gun, and heat treated at 165° C. in AirO'En to form a coating film. Forms a uniform brown coating with a coating thickness of 15μ
The bending strength was also sufficient. In addition, instead of using a spray gun, it was possible to apply with a bar coater or brush in the same way as with regular paint.

Example 2 5.45 kg of polyethylene having a density of 0.910 and [η]20.55 and 0.55 kg of anhydrous maleic-resistant grafted polyethylene wax having an acid value of 50 were melt-mixed at 170°C.

Water 60Z, . 18.8 g of Na0H was added, heated to 150° C., and the molten mixture was charged with a gear pump for 3 hours while stirring at 500 rpm. After further stirring for 30 minutes, the concentration of the aqueous dispersion obtained by slowly cooling to room temperature was 100 g/1
The viscosity was 5 cps (25° C.), and the particles were spherical with an average particle size of 2 μm. This polyolefin dispersion 11
A dispersion liquid was produced in the same manner as in Example 1 by adding the polyvalent metal salts shown in Table 2 to the dispersion.

Claims (1)

[Claims] 1. 50 to 95 parts by weight of polyolefin and an acid value of 3
A polyolefin composition comprising 5 to 50 parts by weight of a polyvalent metal salt of a polyolefin wax containing 0 to 150 carboxyl groups, and the amount of the polyvalent metal present as the salt is 0.01 to 1.0 meq/g composition. Particle size of 0.
5 to 100μ aqueous dispersion. 2 50 to 95 parts by weight of polyolefin and acid value 3
It is characterized by contacting a water-soluble polyvalent metal salt with an aqueous dispersion of a polyolefin composition having a particle size of 0.5 to 100μ and comprising 5 to 50 parts by weight of an alkali metal salt of a polyolefin wax containing 0 to 150 carboxyl groups. A method for producing an aqueous dispersion according to claim 1.