JPS5811460B2 - 1,2- Polybutadiene - Google Patents

Description

[Detailed description of the invention] This invention modifies a 1,2-polybutadiene molded product,
The present invention relates to a method for producing molded articles with excellent transparency and mechanical properties.

More specifically, the present invention provides a method for producing a 1,2-polybutadiene molded article having a vinyl structure content of 70 degrees or more and a melting point of 70 degrees Celsius or more under non-oxidizing conditions at a temperature in the range of 200 to 400 degrees Celsius.
Heating the molded product until its density is 0.93 g/cm3 or more, and during the above heating, the molded product must be heated in a cavity corresponding to its shape until the gel fraction of the molded product reaches at least 30 cm. This is a method for modifying a 1,2-polybutadiene molded product, which is characterized by holding the molded product in a mold having the following properties.

In this specification, gel fraction refers to the weight of the pulverized product obtained by pulverizing the heated molded product, subjecting the pulverized product to Soxhlet extraction using xylene for 8 hours, and vacuum drying at 40°C for 45 hours. It is a percentage of the weight of the ground material before Soxhlet extraction.

1.2-Modification methods for polybutadiene molded products include 1.
A method of irradiating 2-polybutadiene with ionizing radiation is known.

However, the molded articles obtained by this method have poor transparency, and the improvement in mechanical properties is not so remarkable.

An object of the present invention is to provide a method for modifying a 1,2-polybutadiene molded article to produce a molded article with excellent transparency and mechanical properties.

In this invention, 1,2-polybutadiene, which is the raw material for the 1,2-polybutadiene molded product, has a vinyl structure content of 70 or more, preferably 85 or more, and a melting point of 7.
A temperature of 0°C or higher is used.

If 1,2-polybutadiene with a vinyl structure content lower than 70% is used, only molded products with poor transparency and poor mechanical properties can be obtained.

Known antioxidants and heat stabilizers may be added to 1,2-polybutadiene before molding.

In this invention, the 1,2-polybutadiene molded product is
, 2-polybutadiene by compression molding, injection molding or extrusion molding.

These 1,2-polybutadiene molded products are heated under non-oxidizing conditions at 200 to 400°C, preferably 250 to 350°C.
At a temperature in the range of °C, the density of the molded article is 0.93 g/cm3
It is preferably heated until it reaches 0.95 g/cm3 or more.

When heating the molded article, it is necessary to hold the molded article in a mold having a cavity corresponding to its shape until the gel fraction of the molded article reaches at least 30.

Methods of heating the molded product include a method of continuously heating the molded product in a mold having a cavity corresponding to the shape of the molded product until the density of the molded product reaches 0.93 g/cm3 or more; In a mold having a cavity corresponding to the shape, the molded product is heated to infusible until the gel fraction becomes at least 30 cm, and then the molded product is removed from the mold and heated under an inert gas atmosphere. Any method of heating the molded article in a salt bath, oil bath, or metal bath until the density of the molded article reaches 0.93 g/Cm3 or more may be employed.

In the latter method, a molded article with a gel fraction lower than 30 parts cannot melt and maintain its shape during subsequent heating, so the gel fraction of the molded product is at least 30 parts. Until then, it is necessary to heat the molded article in the mold.

In the present invention, when a 1,2-polybutadiene molded article is manufactured by compression molding or injection molding, the mold used for manufacturing the molded article can be used as it is as a mold for heating.

That is, a molded article having a desired shape can be manufactured by compression molding or injection molding, and then the molded article can be heated by maintaining the mold at a predetermined temperature.

When producing a 1,2-polybutadiene molded product by extrusion molding, a mold having a cavity corresponding to the shape of the desired molded product is separately manufactured, and the molded product is placed in this mold and heated.

Heating of the molded product is from 200 to 400°C, preferably from 250 to
It is carried out at a temperature in the range of 350°C.

If the heating temperature is lower than 200°C, it will take a long time to modify the molded product, and if the heating temperature is higher than 400°C, thermal decomposition of the molded product will occur, which is not preferred.

Heating of the molded article must be carried out under non-oxidizing conditions to prevent coloring of the molded article and deterioration of physical properties of the molded article due to oxidation.

When heating to the end in the mold, it is necessary to sufficiently remove air from the cavity in advance.

In addition, if the molded product is heated in the mold until its gel fraction reaches at least 30%, then taken out of the mold and continued heating, thoroughly remove the air in the cavity using the same method as above. The molded article is then heated in a mold, and then the molded article is heated in an inert gas atmosphere, a salt bath, an oil bath or a metal bath.

1.2-When a polybutadiene molded product is heated, it cyclizes and crosslinks, shrinks and increases its density, but when the density of the molded product is 0
．． 93g/cm3 or more, preferably 0.95g/cm3
It is necessary to continue heating the molded product until the temperature reaches this point.

Molded articles having a density after heating of less than 0.93 g/cm3 have low transparency and insufficient mechanical properties.

Next, Examples and Comparative Examples will be shown.

In the Examples and Comparative Examples, the bending strength and bending modulus are ASTM D790-71, and the Shore hardness is ASTM D790-71.
Measured with TM D1706-61.

The degree of haze was measured using a Poitzk integrating sphere haze meter (manufactured by Nippon Seimitsu Kogyo), and the density was measured using a density gradient tube using a mixed solution of water and n-propyl alcohol.

Example 1 Vinyl structure content 88%, melting point 144°C, density 0.91
Pellets prepared by blending 0.2 parts by weight of 2,6-di-tert-butyl-p-cresol with 100 parts by weight of 1,2-polybutadiene at 6 g/cm3 were charged into the cavity of a compression molding machine and sufficiently deaerated. A sheet with a thickness of 5 mm was produced by compression forming at 100 kg/cm 2 at 100° C. for 10 minutes.

The gel fraction of this sheet is 76.3% and the bending strength is 128
kg/cm2, bending elastic modulus is 1,796 kg/cm2
, Shore hardness is 56, color is milky white, density is 0.91
It was 9g/cm3.

This sheet was immersed in a salt bath at 300° C. for a predetermined period of time, and the physical properties of the obtained sheet were measured.

The results are shown in Table 1.

Comparative Example 1 The pellet used in Example 1 was heated to 150℃100kt4
/cm2 for 10 minutes and the physical properties of the sheet obtained were measured.

The bending strength of this sheet is 149ky/cm2. The bending elastic modulus is 2,133ky/cm2. The Shore hardness (D scale) was 57, the density was 0.917 g/cm3, and the color of the sheet was milky white.

Comparative Example 2 A sheet obtained in the same manner as in Example 1 except that the heating time in the salt bath was changed to 10 minutes had a density of 0.9239/cm3.
The bending strength is 45 to 9/cm2. Flexural modulus is 546ky
/cm3. Shore hardness (D scale) is 45,
The color tone of the sheet was milky white.

Example 2 Table 2 shows the physical properties of a sheet obtained in the same manner as in Example 1, except that the compression molding temperature was changed to 300°C.

The gel fraction of the sheet after compression molding was 78.5 inches.

Example 3 A sheet was produced by compression molding at 300° C. and 100 ky/cm 2 in the same manner as in Example 2, and the sheet was held in the mold for a predetermined period of time. Table 3 shows the physical properties obtained.

In addition, in Table 3, the heating time is the time after starting compression molding.

Claims (1)

[Claims] 1 Vinyl structure content of 70% or more, melting point of 70℃ or more 1
, 2-polybutadiene molded product under non-oxidizing conditions.
The density of the molded product is 0.93 at a temperature in the range of 0 to 400℃.
g/cm3 or more, and during the above heating, the molded product is placed in a mold with a cavity corresponding to its shape until the gel fraction of the molded product reaches at least 30 ml. 1. A method for modifying a 1,2-polybutadiene molded product, characterized by retaining.