JPS6260401B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing chlorinated polyethylene rubber for vulcanization in powder form, which has good moldability and has physical, chemical, and electrical insulation properties.

Conventional rubber-like chlorinated polyethylene (CPE)
) has good heat resistance, weather resistance, chemical resistance, oil resistance, flame resistance, ozone resistance, electrical insulation properties, etc., and is easy to handle because the rubber-like CPE itself is in powder form. It has various uses as a rubbery polymeric material, such as impact modifier of PVC, PE,
PP stress cracking improver, PE, PP,
It has been used as a flame retardant for ABS and AS resins, coating materials for electric wires, rubber magnets, and vulcanized rubber products. In either case, the chlorine content is required to improve the physical properties of the product.
25 to 45% by weight, the higher the molecular weight, the better, and usually the MI of the raw material polyethylene is 10g/10min or less.
CPE is preferred. On the other hand, from the viewpoint of processability, it is desirable to use polyethylene with a small molecular weight and narrow distribution as a raw material in order to lower the melt viscosity, but this is inconsistent with the above-mentioned physical properties of the product. Therefore, when CPE is used as a thermoplastic resin, its molecular weight has been selected depending on the respective application. However, when using CPE as a vulcanized rubber product, there is a fundamental defect that crosslinking properties deteriorate when the molecular weight is small, so CPE with a large molecular weight must be used, and therefore it is difficult to use at high temperatures. However, in the rubber processing industry, there are generally few methods of processing at high temperatures, and in most cases, plasticizers and oils have been added during molding to enable processing at low temperatures. As a result, the heat resistance of the finished product,
The use of CPE rubber has been restricted due to oil resistance and other issues.

In recent years, the automobile industry, electrical industry, civil engineering and construction industry, etc. in particular have desired to use inexpensive vulcanized CPE rubber products with excellent ozone resistance, heat resistance, oil resistance, and weather resistance. Therefore, there is a strong desire for a powdered CPE rubber for vulcanization that has improved processability as well as physical properties.

Therefore, in order to obtain rubber-like CPE with good processability even with a large molecular weight, the present inventors conducted various research on methods to reduce the flow resistance of CPE.
As mentioned above, even without adding additives, if polyethylene with a molecular weight distribution (Mw/Mn) of 20 or more is used as a raw material, even if the molecular weight is large (MI1g/10 minutes or less), it will fluidize and melt under pressure at low temperature. The present invention was achieved by discovering that molding becomes easier.

That is, the present invention provides molecular weight distribution (Mw/
Mn) is 20 or more and melt viscosity index (MI) is 1g/10
Chlorinating powdered polyethylene containing 25 to 45% by weight of chlorine and 1% or less of residual crystals using chlorine gas under high-temperature aqueous suspension near the melting point of the crystals. This is a method for producing chlorinated polyethylene rubber for vulcanization in powder form with good molding processability.

The polyethylene used in the present invention has an MI of 1g/10
Among high-molecular-weight polyethylenes having a molecular weight of 20 or less, as long as the molecular weight distribution (Mw/Mn) is 20 or more and the density is 0.92 or more, the manufacturing method may be high pressure, medium pressure, low pressure, gas phase, liquid phase, etc. Further, as long as the density is 0.92 or more, ethylene alone or a copolymer of a small amount of propylene, butene, pentene, acrylic ester, etc. may be used.

MI is 1 from the viewpoint of cross-linking reactivity and physical properties of the product.
g/10 minutes or less is desirable. If it exceeds 1 g/10 minutes, crosslinking will be slow and the tensile strength, oil resistance, etc. will decrease, which is not preferable.

The density depends on the type and amount of polyethylene crystals and copolymer monomers, but if it is less than 0.92, blocking will easily occur during aqueous suspension chlorination and is not suitable.

The most important feature of the present invention is the molecular weight distribution,
The wider the width, the better the workability. Until the present invention, the concept of molecular weight distribution had not been considered for CPE, and it was thought that the narrower the distribution, the lower the melt viscosity at high temperatures, which is preferable. In other words, the main use of CPE in the past was as a performance modifier for thermoplastic resins, and this is thought to be because it was often used in extruders and injection machines, which made it easy to reach high temperatures. Therefore, the present invention breaks the conventional wisdom. The reason why low-temperature processability improves when the distribution is wide may be explained by the destruction of the structural viscosity, but this has not yet been elucidated. In addition, if the molecular weight distribution of polyethylene with an MI of 1 g/10 min or less becomes extremely broad, the low molecular content will increase, and it will probably become difficult to chlorinate, and its physical properties will also deteriorate, but the upper limit of the distribution is practical. A value of 50 or less is considered sufficient for this purpose. However, the industrialization of polyethylene with an MI of 1 g/10 minutes or less and a distribution of 20 or more is relatively new. Most conventional polyethylenes have a molecular weight distribution of about 10 to 15 or less.

The molecular weight distribution (Mw/Mn) of polyethylene is 0.1 in the solvent 1,2,4-trichlorobenzene.
It is the ratio of weight average molecular weight (Mw) and number average molecular weight (Mn) based on polystyrene as measured by gel permeation chromatography at 135°C for a weight percent solution. The detector used for the measurement is a differential refractometer.

To carry out the invention, the polyethylene defined above must be chlorinated in aqueous suspension near the melting point of the polyethylene, with a chlorine content of 25 to 45% by weight and a residual crystal content of less than 1%. 1%
CPE with residual crystals exceeding 50% has a high modulus and low rubber elasticity at low temperatures, making it undesirable. Furthermore, even if there are few remaining crystals, if the chlorine content is high, it will become hard and unfavorable in terms of physical properties. Therefore, it is important to break the crystals with as little chlorine as possible in rubbery CPE.
It is necessary for production, and for this purpose, in the aqueous suspension method, chlorination must be carried out at a high temperature as close to the melting point of polyethylene as possible. Such techniques are known and have very high MI or low density.
This technique is relatively easy, except in cases where it is less than 0.92, has stickiness even at low temperatures, and is easily agglomerated, making aqueous suspension chlorination difficult.

On the other hand, the polyethylene with a large molecular weight distribution used in the present invention includes low molecular weight polyethylene. Therefore, chlorination near the melting point of polyethylene tends to cause fusion and agglomeration of polyethylene particles, and chlorination requires a high degree of care and skill. That is, a multi-stage process for producing chlorinated ethylene, including a method in which the chlorination temperature is changed in stages according to the degree of chlorination, and, if necessary, a heat treatment step under conditions in which chlorine gas is not supplied during chlorination ( For example, Special Publication No. 47-7896, Special Publication No. 49-9111,
USP No. 3759888, etc.).
These will be explained in detail with reference to Examples. When fusion and agglomeration occur due to chlorination, the subsequent chlorination reaction, furthermore, the removal of hydrochloric acid water from CPE,
Drying becomes difficult. The particle size of the powdered CPE obtained by the present invention varies depending on the particle size of the raw material polyethylene, but is preferably 0.5 mm or less on average. Powdered CPE rubber with such a particle size is easy to handle during molding, powder transfer, additive blending, etc., and is preferred for processing.

The chlorinated polyethylene of the present invention can be used with various known rubber compounding agents, such as dicumyl peroxide and other peroxide vulcanizing agents, trithiocyanuric acid and other triazine vulcanizing agents, and various other vulcanizing agents; Nurate, dicyclohexylamine 2-benzothiazole, and various other vulcanization aids; Magnesium oxide, lead oxide, and other various acid acceptors; Titanium oxide, carbon black, talc, and other various fillers or coloring agents; Anti-aging agents; Stabilizers: DOP, TOPM, various other plasticizers, calcium stearate, various other processing aids, etc. are blended in appropriate amounts to form a rubber composition, and the rubber composition is vulcanized according to a conventional method to form a vulcanizate. Can be done.

These compositions may be mixed using a mixer commonly used in the technical field such as an open roll, dry blender, Banbury mixer, or kneader. One of the features of the present invention is that when mixing using a machine, the mixing time is short and less power is required.

Moreover, the CPE of the present invention and these compositions are
It can be molded into a desired shape using molding machines such as extrusion molding machines, injection molding machines, compression molding machines, and calendar molding machines that are commonly used in the general rubber and resin industries. Another feature of the present invention is that it can be made into a molded product with a beautiful surface texture. This means that, for example, when extruding hoses, electric wires, etc., molding can be performed at a higher speed than conventional CPE, which has a large economic effect.

This will be explained below using examples.

Example 1 MI=0.05g/10min, Mw/Mn=30, density=
0.955, 5 kg of low-pressure polyethylene powder with a DSC method crystal melting point of 128°C, 40 mesh or less, was placed in a 100-liter autoclave, ion-exchanged water 70, wetting agent 2 g,
After adding 200ml of dispersant and chlorinating at 106°C to a chlorine content of 20% by weight as the first step, the chlorine gas was expelled and the chlorine was cut off at 128°C.
After stirring only for 1 hour at .degree. C., chlorination was carried out at the same temperature until the chlorine content was 35% by weight. After cooling, wash,
Dry. The average particle size of this CPE was 0.1 mm. The crystal density determined by DSC measurement was 0ca1/g.
Also, the viscosity of this CPE toluene 10% by weight solution (23
°C) was 18×10 ³ cps. By heating a regular rubber kneading roll (6 inches in diameter) to 40°C and passing through the kneading section three times, this powdered CPE was gathered into a sheet and kneaded in about 5 minutes. When carbon was further added to the sheet, it was immediately absorbed into the sheet and did not fall off the roll.

In addition, 100 parts of this CPE (parts by weight, same hereinafter),
Carved die test with 30 parts of carbon (SRF) (Equipment used: Brabender, cylinder diameter 19 mm,
L/D10, compression ratio 1, rotation speed 30rpm, temperature cylinder 75℃, die 80℃), discharge pressure 20~30
A molded product with a smooth surface was obtained at Kg/cm ² .

In addition, for 100 parts of this CPE, 30 parts of carbon (SRF), 2.5 parts of dicumyl peroxide as a crosslinking agent, 2.5 parts of triallylisocyanurate,
After adding 10 parts of Resurge and kneading with a roll at 40°C for 5 minutes, the mixture was hot pressed at 160°C for 20 minutes to perform a crosslinking reaction. The physical properties of the vulcanizate are hardness 70 and tensile strength
205Kg/cm ² , elongation 300%, oil resistance test [JIS3
No. 1 oil at 120°C for 3 days] showed a weight increase rate of 52%, indicating sufficient crosslinking.

Comparative example 1 MI=6.5g/10min, Mw/Mn=5, density=
A powder of 40 mesh or less of low-pressure polyethylene having a melting point of 0.956 and a DSC crystal melting point of 126°C was chlorinated under the same conditions as in Example 1 to a chlorine content of 35% by weight to obtain powdered CPE (average particle size 0.2 mm). The toluene 10% by weight solution viscosity (23°C) of this CPE was 11×10 ³ cps, which was the same as in Example 1.
Even though it was smaller than CPE, the roll temperature needed to be 80° C. or higher to form it into a sheet using the same 6-inch roll as in Example 1.

In addition, the crosslinking reaction was carried out using a hot press in the same manner as in Example 1, but the oil resistance test [JIS No. 3 oil 120°C x 3 days]
It was found that the weight increase rate was 130%, indicating poor crosslinking properties.

Comparative example 2 MI=0.045g/10min, Mw/Mn=12, density=
0.956, low pressure polyethylene with a DSC method melting point of 128℃
Powder of 40 mesh or less was chlorinated under the same conditions as in Example 1 to a chlorine content of 35% by weight to form a powder (average particle size 0.1
mm) obtained CPE. The crystal content of this CPE was 0 cal/g by DSC measurement.

In the Garbe die test, the molded product was not discharged under the same conditions as in Example 1, so a molded product was obtained at a discharge pressure of 40 to 50 kg/cm ² with a formulation containing 15 parts of plasticizer (DOP), but only a molded product with a rough surface was obtained. Nakatsuta. Also this
A temperature of 110°C or higher was required to form CPE into a sheet using a 6-inch roll.

Example 2 A powder of 40 meshes or less of low-pressure polyethylene with MI=0.07 g/10 min, density=0.951, molecular weight distribution (Mw/Mn)=26, and DSC crystal melting point of 127°C was prepared in Example 1.
was chlorinated under the same conditions as , and the chlorine content was 40% by weight. The viscosity of a 10% toluene solution (23°C) of the CPE was 30×10 ³ cps. Also 6 at 40℃
Easily kneaded with inch kneading rolls. Further, a crosslinking reaction was carried out in the same manner as in Example 1, and the value of the heat resistance test [JIS No. 3 oil 120°C x 3 days] was 21% in weight increase rate, indicating that the crosslinking property was good.

Claims (1)

[Claims] 1. Powdered polyethylene with a molecular weight distribution (Mw/Mn) of 20 or more and a melt viscosity index (MI) of 1 g/10 min or less is suspended in aqueous suspension at a high temperature near the melting point of its crystals, using chlorine gas to remove chlorine. A method for producing chlorinated polyethylene rubber for vulcanization in powder form with good moldability, characterized by containing 25 to 45% by weight of chlorinated polyethylene rubber and chlorinating so that residual crystals are 1% or less.