JPS60250048A - Pre-expanded propylene resin particle - Google Patents

Abstract

PURPOSE:To provide pre-expanded propylene resin particles having excellent low-temperature moldability, flexibility, etc., by using a resin mixture of a crystalline random propylene copolymer and an atactic propylene resin in a specified weight ratio as a base resin. CONSTITUTION:80-99wt% crystalline random propylene copolymer (e.g. a random propylene/ethylene copolymer contg. 95-99wt% propylene) is mixed with 20-1wt% atactic propylene resin. The resulting resin mixture is used as a base resin. For example, a blowing agent (e.g. propane), a dispersant (e.g. basic magnesium carbonate), etc. are incorporated in the base resin particles in a closed vessel. While keeping the pressure within the vessel at not lower than the vapor pressure of the blowing agent, one end of the vessel is opened to thereby expand the resin particles, thus obtaining the desired pre-expanded propylene resin particles.

Description

[Detailed description of the invention] The present invention relates to propylene resin pre-expanded particles.

More specifically, the present invention relates to pre-expanded propylene resin particles that are excellent in low-temperature moldability and flexibility.

It is obtained by filling pre-expanded particles indoors and heating and foaming them. The so-called bead foam molded body (m-type body) has a buffering property,
Excellent insulation properties, cushioning material, packaging material.

It is widely used in insulation materials, construction materials, etc., and the demand for it has increased tremendously in recent years.

Conventionally, molded bodies made of pre-expanded polystyrene particles have been known as this type of molded body, but indoor molded bodies made of pre-expanded polystyrene particles have the fatal disadvantage of being brittle and having poor chemical resistance. Improvements have long been desired.

A molded article made of crosslinked polyethylene pre-expanded particles has been proposed as a solution to these drawbacks. However, in the case of cross-linked polyethylene pre-expanded particles, it is difficult to obtain a low-density (highly foamed) molded product by indoor molding.
If we try to obtain a molded product with a low density, we only get a molded product with poor physical properties such as significant shrinkage, high water absorption, and it has not been possible to obtain a molded product that can be put to practical use.

The present inventors have therefore focused on the excellent physical properties of propylene-based resins, and have been conducting research on indoor molded bodies made of propylene-based resin pre-expanded particles in order to solve the drawbacks of conventional indoor molded bodies. However, in the case of propylene-based resin pre-expanded particles.

Compared to indoor moldings made of pre-expanded polystyrene particles or cross-linked polyethylene pre-expanded particles, it is easy to obtain indoor moldings with low density (Takami #l) that have excellent chemical resistance and compressive strength, and have less dimensional change and water absorption when heated. On the other hand, pre-expanded propylene resin particles require a high molding vapor pressure during molding, and the resulting in-mold molded product is not always sufficiently flexible, leaving room for improvement. .

The present inventors conducted intensive research to solve these problems, and as a result, we created a resin made by mixing a crystalline propylene-based random copolymer and an atactic propylene-based resin in a specific ratio as a base resin. The pre-expanded particles have low-temperature moldability,
They discovered that it has excellent flexibility and completed the present invention.

That is, the present invention is a crystalline propylene random copolymer 80
~99 weight ratio and atactic propylene resin 20~
The gist of the present invention is to provide pre-expanded propylene-based resin particles characterized by using a mixed resin of 1% by weight as a base resin.

The crystalline propylene random copolymer used in the present invention has a propylene component of 99 to 90% by weight.
Crystalline glopylene-ethylene random copolymer containing about 90 to 50% by weight of 7'rohylene component, crystalline propylene-1-butene 2 random copolymer containing about 90 to 50% by weight of 7'rophylene component, 99 to 85% by weight of propylene component Among them, a propylene-ethylene random copolymer containing 95 to 99% by weight of a propylene component is particularly preferred.

The atactic propylene resin used in the present invention is crystalline and is obtained as a by-product during the production of propylene resin. Main examples include polymers such as propylene resins having an atactic structure. For example, when producing a propylene resin by a slurry polymerization method using hegetane as a solvent, the polymer is dissolved in heptane and subjected to centrifugation or the like.

It can be obtained by recovering and distilling the solvent from which the produced crystalline propylene resin is separated. Atactic propylene resin wires, globylene homopolymers, and propylene-ethylene block copolymers obtained as by-products during the production of crystalline propylene resins.

Different types of crystalline propylene resins, such as propylene-ethylene random copolymers, are produced as by-products with different compositions.

Particularly preferred are those produced as by-products during the production of crystalline propylene-ethylene block copolymers.

In the pre-expanded particles of the present invention, a mixed resin of 80 to 99% by weight of the above-mentioned crystalline propylene random copolymer and 20 to 1% by weight of atactic propylene resin is used as a base resin. Propylene random copolymer 85
~99% by weight and atactic propylene resin 15~
It is preferable to use a mixed resin with 1 weight percent as the base resin. In the case of pre-expanded particles in which the atactic propylene resin in the base resin exceeds 20 K by weight, the in-mold molded product obtained by molding the pre-expanded particles will have poor dimensional accuracy.]
In addition, in the case of pre-expanded particles having a weight of less than 1 weight Z, low-temperature moldability and flexibility are both unfavorable.

In the pre-expanded particles of the present invention, the base resin may be crosslinked or non-crosslinked; however, when the base resin is non-crosslinked, the pre-expanded particles have a DSC curve obtained by differential scanning calorimetry. The DSC curve obtained when high-temperature peaks 1 to 3 WLII were heated to 220°C at a heating rate of 10°C/min using a differential scanning calorimeter on the high temperature side of the characteristic peak unique to the propylene resin of the material resin. 1. For example, the first DSC curve is the DSC curve obtained when the sample is heated from room temperature to 220°C at a heating rate of 10°C/min. 2.
The second DSC curve is the DSC curve obtained when the temperature is lowered from 20 °C to around 40 °C at a cooling rate of 10 °C / min, and then raised again to 220 °C at a temperature increase rate of 10 °C / min,
From these DSC curves, unique peaks and high temperature peaks can be distinguished.

That is, the above-mentioned characteristic peak is an endothermic peak unique to the propylene resin.

This is thought to be due to the so-called endothermic effect during melting of the crystal. Usually, the characteristic peak appears in both the first DSC curve and the second DSC IIIm, and the temperature at the top of the peak may be slightly different between the first and second times, but the difference is less than 5 degrees Celsius. 1. Constantly below 2°C.

On the other hand, the above-mentioned high temperature peak is an endothermic peak that appears on the high temperature side of the above-mentioned characteristic peak in the first DSC curve,
The pre-expanded particles for which this high temperature peak appears in DSCIIIM have a high compression hardness and compression set rate.

It is possible to provide a molded body with excellent physical properties such as low water absorption. The above-mentioned high-temperature peak whine is thought to be due to the presence of a crystal structure different from the structure that appears as the above-mentioned characteristic peak, and the high-temperature peak appears in the first DSC50 curve, but in the second DSC curve in which the temperature was raised under the same conditions. It does not appear on the curve.

The pre-expanded particles of the present invention are prepared by combining 80 to 99% by weight of the above-mentioned crystalline propylene random copolymer and 20 to 1% by weight of atactic propylene resin, for example, in a closed container with a foaming agent and a mixture of resin particles. ! Depending on the conditions, the particles are dispersed in a dispersion medium such as water together with a dispersant, heated to a temperature higher than the temperature at which the particles soften, and the blowing agent is incorporated into the particles. It is manufactured by a method such as foaming the particles by opening one end of the container while maintaining the pressure higher than the pressure above, and releasing the resin particles and dispersion medium into a low-pressure atmosphere inside the container. Ru.

Furthermore, pre-expanded particles having a crystal structure in which a high-temperature peak appears on the DSC curve can be obtained by dispersing resin particles and a volatile blowing agent in a dispersion medium in a closed container and heating the particles to a temperature higher than the temperature at which the particles soften. At the melting end temperature of the additive resin,
Samples 6 to 8wJF were heated to 220°C at a temperature increase rate of 10°C/min using a differential scanning calorimeter, then cooled to around 40°C at a cooling rate of 10°C/min, and then heated again at 10°C/min. The temperature was increased to 220° C. at a temperature increase rate, and the tail of the endothermic peak of the DSC curve obtained by the second temperature increase was on the high temperature side.

Examples of the blowing agent used in the production of the pre-expanded particles of the present invention include volatile blowing agents such as propane, butane, pentane, cyclobutane, cyclopenkune, tovprolo70lomethane, cyclorosia0lomethane, dichlorotetrafluoroethane, etc. Usually, 5 to 40 parts by weight are used per 100 parts by weight of resin particles. Examples of the dispersant include finely divided aluminum oxide, titanium oxide, basic magnesium carbonate, basic zinc carbonate, calcium carbonate, etc., and the dispersant is 100 parts by weight of resin particles! 70.01 to 10 parts by weight are used.

Expansion of the pre-expanded particles of the present invention obtained as described above 1 For example, after ripening at a predetermined temperature and normal pressure, if necessary, volatile foaming with an inorganic gas such as Il, nitrogen, or air or an inorganic gas at a predetermined temperature. Pressure treatment is performed at a predetermined pressure using a mixed gas with the agent, and then internal pressure is applied, and then the mold is filled into a mold for example 2.
By heating and foaming with water vapor of ~skg/cd (G), a molded indoor molded body can be obtained. The thus obtained in-mold molded body can be used for packaging materials, cushioning materials, vehicle components, building materials, food containers, heat insulating materials, flotation materials, toys, and the like.

As explained above, in the pre-expanded particles of the present invention, the base resin is 80 to 99% by weight of a crystalline propylene random copolymer.
and 20 to 1% by weight of an atactic propylene resin, it maintains the excellent physical properties of conventional propylene resin pre-expanded particles, and also has excellent low-temperature moldability, making it easier to produce in-mold products. It is easy to manufacture and has advantages such as excellent energy efficiency during manufacturing. In addition, the in-mold molded product obtained using the pre-expanded particles of the present invention has a smaller shrinkage rate and greater flexibility than conventional products, with I/1 (
It has excellent physical properties such as strong stiffness.

Hereinafter, the present invention will be explained in more detail by giving Examples and Comparative Examples.

Examples 1-4. Comparative Examples 1 to 2 Resin particles obtained by melt-kneading the crystalline propylene-based random copolymer shown in Table 1 and an atactic propylene-based resin in an extruder, and then extruding it through the extruder and cutting it into pellets. 100 parts by weight, 300 parts by weight of water, 0.3 parts by weight of finely divided aluminum oxide, and 0.3 parts by weight of dicumyl peroxide.
48 parts by weight and 1.0 parts by weight of divinylbenzene were blended in a closed container, heated to 100°C with stirring and held at that temperature for 1 hour, then heated to 150°C and held for 1 hour. It was then cooled down. Table 1 also shows the results of measuring the gel fraction of the resin particles at this time (weight percentage of xylene insoluble matter when the resin particles were boiled in boiling xylene for 8 hours).

Next, 300 parts by weight of water, 0.3 parts by weight of finely divided aluminum oxide, and 17 parts by weight of dichlorosiftetramethane are added to 100 parts by weight of the resin particles in a closed container, and the mixture is heated while stirring to foam the resin particles. After impregnating the agent, the pressure inside the container was reduced to 40 floors/d (G
), one end of the container was opened, the resin particles and water were released under atmospheric pressure, and the resin particles were foamed to obtain pre-expanded particles. Table 2 shows the expansion ratio of the obtained pre-expanded particles.

Then each pre-expanded particle obtained was 3QQmX300sm
The mixture was filled into a mold with an internal dimension of 50 m and heated with steam at various pressures to perform molding. The minimum vapor pressure (minimum moldable vapor pressure) required to obtain a molded product with good particle-to-particle fusion was determined from the results of examining the adhesion of foamed particles to each other in the obtained in-mold molded product. Shown in Table 2. Also, it can be molded using water vapor with the lowest steam pressure.

The 211th physical properties of the molded product obtained by molding! Shown below.

Examples 5-8. Comparative Examples 3 to 4 After melt-kneading the crystalline propylene-based random copolymer shown in Table 3 and atactic glupylene-based resin in an extruder, the extruder extruded the resin and cut it into pellets to form resin particles. Obtained. of this resin particle.

The melting end temperature Tm determined by differential scanning calorimetry is also shown in Table 3.

Next, 300 parts by weight of water, 0.3 parts by weight of finely divided aluminum fluoride, and 17 parts by weight of dichlorodifluoromethane were added to 100 parts by weight of the resin particles in a closed container, and the maximum temperature shown in Table 4 was as follows: After maintaining the foaming temperature T('C) shown in the same table for 30 minutes through Tmaz(t), the container was heated at the same temperature while keeping the pressure inside the container at 4oyu/d(G) using nitrogen gas. One end was opened, the resin particles and water were released under atmospheric pressure, and the resin particles were foamed to obtain pre-expanded particles. Table 4 shows the expansion ratio of the obtained pre-expanded particles and the results of confirming the presence or absence of a high temperature peak in the DSC curve obtained by differential scanning calorimetry of the pre-expanded particles. Further, the DSC curve of the pre-expanded particles of Example 5 is shown in FIG. still,
The solid line in Figure 1 is the first DSC curve.

The dotted line shows the second DSC curve, ad shows the high temperature peak, and b shows the characteristic peak, respectively.

The obtained pre-expanded particles were then molded in the same manner as in Examples 1 to 4 and Comparative Examples 1 to 2. Table 4 also shows the physical properties of the molded bodies obtained by molding at the lowest moldable vapor pressure and the steam at the lowest moldable steam pressure.

*1 Atactic propylene resin I: Atactic propylene resin produced as a by-product during the production of ethylene-propylene block copolymers Atactic propylene-based resin I: Atactic tetrapylene resin produced as a by-product during the production of ethylene-propylene random copolymers Propylene resin ■: Atactic propylene resin produced as a by-product during the production of propylene homopolymer *2 The shrinkage rate of the obtained in-mold molded product in the plane direction of the mold was measured.

Shrinkage rate is less than 2% - 11 ---- 〇1 2% or more and less than 4% - 11111 △ 4% or more □ - -
--- Determined as X.

*3 When a sample cut into a rectangular parallelepiped with a thickness of 20m, a length of 3QOo+, and a width of 40 is bent in a direction so that both sides of 300fi are facing each other, it will not break unless it is bent by 15σ or more---0120'
It was judged as 1111 which can be broken between 150° and 1111 which can be broken at less than △120＠---x.

*4 Measured according to JIS K-6767B method)

[Brief explanation of drawings]

FIG. 1 is a DSC curve of the pre-expanded particles of Example 5. Figure 1

Claims (1)

[Claims] Pre-expanded propylene resin particles characterized in that the base resin is a mixed resin of 80 to 99% by weight of a crystalline propylene random copolymer and 20 to 1% by weight of an atactic propylene resin.