JPH06872B2 - Ethylene copolymer aqueous dispersion - Google Patents

Description

TECHNICAL FIELD The present invention relates to an ethylene copolymer aqueous dispersion.

According to the present invention, it is possible to provide an ethylene copolymer aqueous dispersion which can be used in a wide range of applications such as adhesives and paints, and which is extremely excellent in workability that has a low viscosity even at a high resin concentration. You can

Prior Art A water-dispersible ethylene copolymer containing ethylene and an α, β-unsaturated carboxylic acid is disclosed in JP-A-52-109545,
It is publicly known such as Japanese Patent Laid-Open No. 53-59789, but when the aqueous dispersion of these copolymers is applied to the substrate, it is desirable that the viscosity of the aqueous dispersion is in an appropriate range in order to apply the workability. It is said that.

Generally, when the resin concentration in the aqueous dispersion is increased, a thick coating film can be obtained, which is also preferable from the viewpoint of energy saving,
When the resin concentration is high, there is a problem in that the viscosity of the aqueous dispersion is extremely increased.

As a method for improving this point, for example, JP-A-55-843.
Although a method disclosed in Japanese Patent No. 28 has been proposed,
In such a method, it is necessary to blow carbon dioxide gas, and there has been a demand for a method that can more easily solve the above problems.

SUMMARY OF THE INVENTION The present invention provides an ethylene copolymer aqueous dispersion obtained by dispersing an ethylene copolymer consisting of ethylene and acrylic acid in water using a base, wherein the Q value of the ethylene copolymer (weight average molecular weight / The number average molecular weight) is in the range of 2.0 to 3.0, and the crystallization temperature and the melting temperature are as follows: 35 ° C. ≦ (crystallization temperature) ≦ 1.2 × (melting temperature) −40 ° C. and (melting temperature) ≦ 90. The present invention provides an ethylene copolymer aqueous dispersion characterized by being in the range shown in ° C.

EFFECTS OF THE INVENTION The aqueous ethylene copolymer dispersion of the present invention has a low viscosity over a wide concentration range and is excellent in workability even when an aqueous dispersion having a high resin concentration is used, and a good coating film is obtained. To be

It is totally expected that the above-mentioned excellent effects can be obtained by using the specified ethylene copolymer in the range of the Q value of the ethylene copolymer used and the ranges of the crystallization temperature and the melting temperature. It was not done.

DETAILED DESCRIPTION OF THE INVENTION The ethylene copolymer used in the present invention is an ethylene copolymer composed of ethylene and acrylic acid.

The ethylene copolymer used in the present invention contains 97 to 85 mol% of ethylene, 3 to 15 mol% of acrylic acid, preferably 95 to 85 mol% of ethylene, and 5% of acrylic acid.
˜15 mol%.

The copolymer used in the present invention is produced by subjecting a predetermined monomer to a copolymerization condition, and can be produced by a high-pressure polyethylene production apparatus.

The above copolymer is produced by radical polymerization. Therefore, the catalyst used in the production of the copolymer used in the present invention is a compound which generates a free radical.

For example, ditertiary butyl peroxide, tert-butyl cumyl peroxide, dialkyl peroxide such as dicumyl peroxide, acetyl peroxide, isobutyl peroxide, diacyl peroxide such as octanoyl peroxide, diisopropyl peroxydicarbonate, Peroxydicarbonates such as di2-ethylhexyl peroxydicarbonate,
Peroxy ester such as tert-butyl peroxyisobutyrate, tert-butyl peroxypivalate, tert-butyl peroxylaurate, tert-butyl peroxyneodecanoate, ketone such as methyl ethyl ketone peroxide, cyclohexanone peroxide Peroxyketals such as peroxides, 1,1 vista-sialybutylperoxycyclohexane and 2,2 vista-sialybutylperoxyoctane, hydroperoxides such as tert-butyl hydroperoxide and cumene hydroperoxide, 2 , 2 Azo compounds such as azobisisobutyronitrile.

This polymerization is preferably carried out continuously. As the polymerization apparatus, a continuous stirring tank reactor or a continuous tube reactor which is generally used in a high pressure radical polymerization method of ethylene can be used.

The polymerization can be carried out as a single-zone process using these single reactors, but many reactors can be used in series, optionally with a cooling device, or internally in a multi-zone process. It is also possible to use a single reactor in which the is effectively divided into several zones. In the multi-zone method, the reaction conditions in each zone are made different to control the characteristics of the polymer obtained in each of those reactors or each zone, so that the monomer in each reactor or zone is controlled. It is common to adjust the composition, catalyst concentration, molecular weight modifier concentration, etc. When a plurality of reactors are connected in silos, in addition to a combination of two or more tank type reaction groups or two or more tube type reactors, one or more tank type reactors and one or more tubes are used. Combinations with type reactors can also be used.

The polymer formed in one or more reactors can be separated from the unreacted monomer and processed as in conventional high pressure polyethylene manufacture. The unreacted monomer mixture is mixed with an additional amount of the same monomer,
Repressurize and circulate in reactor. The additional amount of monomer added as described above is of a composition that restores the composition of the mixture to the original composition of the feed, and generally this additional amount of monomer is the weight separated from the polymerization vessel. It has a composition almost equivalent to that of the coalescence.

The reactor is preferably a tank reactor in order to obtain a copolymer having a uniform composition.

The catalyst is usually dissolved in a solvent having a small chain transfer effect and directly injected into the reactor by a high pressure pump. Concentration is 0.5-3
About 0% by weight is desirable.

Suitable solvents include, for example, hexane, heptane, white spirit, hydrocarbon oils, cyclohexane, toluene, higher branched saturated fatty acid hydrocarbons, and mixtures of these liquids.

Acrylic acid is supplied as it is or after being dissolved in a solvent by a high-pressure pump.

In the high-pressure radical polymerization, a chain transfer agent is generally used for adjusting the molecular weight except for a special case.

As the chain transfer agent, all those used in ordinary high pressure radical polymerization can be used.

For example, alkanes such as ethane, propane, butane, hexane, heptane, alkenes such as propylene, butene, hexane, alcohols such as ethanol, methanol, propanol, ketones such as acetone and methyl ethyl ketone, acetaldehyde, propionaldehyde, etc. Aldehydes, esters such as methyl acetate and ethyl acetate, and many other compounds used in the high pressure method can be used.

These gaseous substances are injected into the suction side of the compressor, and liquid substances are injected into the reaction system by a pump.

It employed the polymerization pressure is a pressure exceeding 500 kg / cm ^2, preferably in the range of 1000~3000kg / cm ^2.

The polymerization temperature is at least 120 ° C, preferably 15
It is in the range of 0 to 300 ° C.

The copolymer produced in the reactor and used in the present invention is separated from the monomer by a separator according to a conventional high pressure radical polymerization method, and is directly used as a product. This product may be used as it is, but may be subjected to various post-treatment steps such as those already used for products obtained by the high pressure radical polymerization method.

The ethylene copolymer thus produced has a Q value (weight average molecular weight / number average molecular weight) of 2.0 to 3.0, preferably 2.0 to 2.7, and more preferably 2.0 to 2.5. And a crystallization temperature and a melting temperature thereof are in the following formulas, 35 ° C. ≦ (crystallization temperature) ≦ 1.2 × (melting temperature) −40 ° C., and (melting temperature) ≦ 90 ° C., preferably Ethylene copolymers within the ranges shown by the following formulas, 40 ° C. ≦ (crystallization temperature) ≦ 1.2 × (melting temperature) −40 ° C. and (melting temperature) ≦ 85 ° C. must be used in the present invention.

Here, the Q value is measured by a known method using gel permeation chromatography (GPC) and a differential refractometer to obtain a weight average molecular weight and a number average molecular weight from a calibration curve using standard (monodisperse) polystyrene. , Calculated from this. The GPC measurement conditions are as follows.

Column: polystyrene gel column (mixed type), 8 mm ^φ × 250 mm × 3 solvent: 1,2,4-trichlorobenzene: acetic acid = 9: 1 (volume ratio) Flow rate: 1 ml / min Temperature: 80 ° C Injection volume: 300 μl Concentration: 3 mg / ml Detector: Differential refractometer The crystallization temperature and the melting temperature were measured by a known method using a differential scanning calorimeter (DSC). The DSC measurement conditions were as follows: Model DSC-2 manufactured by Du Pont Co., Ltd. was used in a nitrogen atmosphere at a sample weight of about 5 mg and at a temperature rising or cooling rate of 10 ° C./min.

An aqueous dispersion is produced using the ethylene copolymer obtained as described above, and the method for producing the aqueous dispersion is described in, for example, JP-A-49-120789 and 52-10954.
The solubilization method of a polymer containing a carboxyl group described in JP-A No. 5 and No. 56-120780, etc. is adopted.

As a preferable method for producing the ethylene copolymer aqueous dispersion of the present invention, water and a base are added to the ethylene copolymer, and the mixture is heated to a melting temperature of the copolymer to 200 ° C. while stirring to obtain an aqueous dispersion. This is a method of obtaining liquid. Here, in order to prevent the corrosion of the device by a base, the melting temperature of the copolymer is about 1
More preferably, it is produced by heating in the range of 20 ° C.

The base used to prepare the aqueous dispersion of the present invention is
So long as it can neutralize the carboxylic acid and does not impair the stability of the aqueous dispersion, it is not particularly limited, but lithium hydroxide, sodium hydroxide, from the viewpoint of practicality,
Alkali metal hydroxides such as potassium hydroxide, organic amines such as methylamine, triethylamine, ethylenediamine and monoethanolamine, and ammonia are preferable.

The amount of the base used depends on the amount of the acid groups contained in the copolymer.
It is an amount that neutralizes 0 mol% or more, preferably 40 to 90 mol%. Generally, the smaller the amount of the base used, the lower the viscosity, but if the amount of the base used is less than 20 mol%, it becomes difficult to produce a stable aqueous dispersion.

If the concentration of the ethylene copolymer of the present invention in the aqueous dispersion is too low, the thickness of the coating after coating is limited, and the amount of water to be sprayed increases, which is not preferable in terms of energy saving, and is too high on the contrary. Since the viscosity of the dispersion is high and the workability during coating is poor, it is generally preferably from 15 to 50% by weight.

The aqueous dispersion of the present invention is characterized in that the ethylene copolymer is neutralized with a base and dispersed in water, but it is generally known to be added to an aqueous dispersion as necessary ( (See, for example, JP-A-57-137337)
Additives such as surfactants, plasticizers, preservatives, defoamers, thickeners, antistatic agents, lubricants, UV absorbers, anti-blocking agents, etc., as well as methanol for the purpose of promoting drying, Ethanol, lower alcohols such as isopropanol, ethylene glycol for the purpose of improving film-forming properties, ethyl ether or butyl ether of ethylene glycol, etc., and also the aqueous dispersion of the present invention for the purpose of cost reduction, control of blocking resistance or adhesiveness, etc. Known aqueous dispersions of compatible polyethylene, polyvinyl acetate, polyvinyl chloride, ethylene-vinyl acetate copolymer, vinylidene chloride, polyacrylic acid and the like can be added.

Experimental Example Reference Example 1 (Production of ethylene copolymer) Using a tank reactor with a stirrer, ethylene, acrylic acid,
Polymerization initiator and chain transfer agent are continuously supplied, polymerization pressure is 1,800 to 2,500 kg / cm ² , and polymerization temperature is 190 to ²
Polymerization was carried out at 30 ° C. to obtain various ethylene-acrylic acid copolymers shown in Table-1. Table 1 shows the physical properties of the obtained copolymer.
It was shown to.

Table 1 also shows the physical properties of commercially available ethylene acrylic acid copolymers.

Example 1 125 g of ethylene copolymer A, 17.2 g of 25% ammonia water, and 357.8 g of distilled water were placed in a tank reactor equipped with a stirrer having an internal volume of 1 and 2 at 100 ° C.
The aqueous dispersion was prepared by stirring for hours.

After leaving the obtained aqueous dispersion at room temperature for 1 week, the viscosity was measured with a B-type viscometer at 230 ° C. and the rotor rotation speed was 20 rp
When measured by M, it showed 40 centipoise.

Examples 2 to 7 and Comparative Examples 1 to 6 An aqueous dispersion was produced in the same manner as in Example 1 except that the type and amount of the ethylene copolymer used and the amount of 25% aqueous ammonia were changed. The viscosity was measured after standing for 1 week at the room temperature. The results are shown in Table-2.

From the results shown in Table 2, the aqueous dispersion of the present invention has a low viscosity over a wide concentration range, and is an excellent aqueous dispersion having a remarkably low viscosity at a resin concentration of 25 wt% which is a commonly used resin concentration. Is clear.

Claims (1)

[Claims] 1. An ethylene copolymer aqueous dispersion obtained by dispersing an ethylene copolymer comprising ethylene and acrylic acid and having an ethylene content of 97 to 85 mol% in water using a base. Q value (weight average molecular weight /
The number average molecular weight) is in the range of 2.0 to 3.0, and the crystallization temperature and the melting temperature thereof are as follows: 35 ° C. ≦ (crystallization temperature) ≦ 1.2 × (melting temperature) −40 ° C. Temperature) ≦ 90 ° C., which is an aqueous dispersion of ethylene copolymer.