JPS5876231A - Method for producing pre-expanded polypropylene resin particles - Google Patents

Abstract

PURPOSE:To improve the moldability and flexibility, by dispersing a polypropylene polymer containing a volatile foaming agent into a dispersion medium in a container, and opening one end of the container while keeping the suspension in the container at a specific temperature, so that the dispersion is released into a low pressure atmosphere. CONSTITUTION:0.08-0.25mol of a volatile foaming agent is incorporated into 100pts.wt. plypropylene polymer partices, and the mixture is dispersed into a dispersion medium in a closed container. While the temperature in the container is kept such that THD+27<T<=THD+45 (where T represents the temperature in the container in deg.C, and THD represents the heat distorsion temperature of the polymer particles in deg.C), one end of the container is opened so that the polymer particles and the dispesion medium are simultaneously released from the container into an atmosphere whose pressure is lower than in the container. As the volatile foaming agent, can be used aliphatic hydrocarbons such as propane, butane, etc., halogenated hydrocarbons such as trifluoromethane, etc. and cycloaliphatic hydrocarbons such as cyclobutane, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing pre-expanded polypropylene resin particles.

The applicant has already proposed a method for producing pre-expanded particles (Japanese Patent Publication No. 56-1344). is dispersed in a closed container, heated to a temperature equal to or higher than the softening temperature of the polymer while maintaining the pressure in the container at the vapor pressure of the blowing agent or higher, and then one end below the water level in the container is opened. However, it is disclosed that highly foamed pre-expanded particles can be obtained by foaming polymer particles and water by simultaneously discharging them into an atmosphere at a lower pressure than in the container. It is used as a material resin. The pre-expanded polypropylene resin particles obtained by the above-mentioned method are highly foamable and have an excellent property of being dense and having a large number of cells per unit area. There is still room for improvement in terms of moldability, shrinkage during molding, flexibility, etc.

The entire purpose of the present invention is to provide a method for producing pre-expanded polypropylene resin particles which are further improved from the pre-expanded particles of the prior art, and the present invention has high foaming properties and moldability. As a result of intensive research to obtain pre-expanded particles with good foaming properties, low shrinkage during molding, and high flexibility (strong stiffness), we have found that pre-expanded polypropylene resin particles with high foaming and appropriate cell diameters meet these objectives. They discovered what could be achieved and succeeded in developing a manufacturing method, thereby completing the present invention.

That is, the present invention involves a step of incorporating 0.08 to 0.25 mol of a volatile blowing agent into polypropylene polymer particles per 100 parts by weight of the polymer particles, and dispersing the polymer particles in a dispersion medium in a closed container. The formula for the temperature inside the Buddha and container is:
THD +27 < T≦T HD+45 (in the formula, T
is the temperature inside the container (°C), and THD is the heat distortion temperature (°C) of the polymer particles. ) Pre-foaming of a polypropylene resin characterized by the step of opening one end of the container while maintaining the temperature within the range expressed by () and simultaneously releasing the particles and dispersion medium into an atmosphere at a lower pressure than the inside of the container. The gist is the method for producing particles.

As the polymer used in the present invention, a polypropylene polymer is used, and specific examples thereof include ethylene-propylene random copolymer, ethylene-propylene block copolymer, propylene homopolymer, etc. However, ethylene-prohylene random copolymer is preferred. These polymers may be crosslinked or non-crosslinked, but non-crosslinked ones are particularly useful.

Volatile blowing agents used in the present invention include, for example, aliphatic hydrocarbons such as propane, butane, pentane, hequinane, heftane, etc.; Halogenated hydrocarbons such as methane, dichlorodifluoromethane, dichlorotetrafluorobethane, methyl chloride, ethyl chloride, and methylene chloride are used. The amount of this blowing agent added is 100 polymer particles.
The amount is 0.08 to 0.25 mol per part by weight.

If the amount added is less than 0.08 mol, only a product with low Ar'fi+ can be obtained, and if it exceeds 0.25 mol, it is not practical because open cells tend to occur.

In the present invention, the timing of incorporating the blowing agent into the polymer particles is not particularly limited. Therefore, the foaming agent may be contained in the polymer particles in advance, and the polymer particles containing the foaming agent may be placed in a closed container and dispersed in a dispersion medium in the closed container, or the polymer particles and the foamed The foaming agent may be contained in the polymer particles while the foaming agent is placed in a closed container and dispersed in the dispersion medium in the closed container (even in the latter case, the polymer particles containing the foaming agent are dispersed in the dispersion medium). (Needless to say, it is distributed). Alternatively, a blowing agent may be introduced into the closed container during or after heating the particles to a predetermined temperature in the closed container, so that the particles contain the foaming agent.

Similarly, the temperature at which the blowing agent is incorporated into the particles is also arbitrary and not particularly limited.

In the present invention, the polymer particles and the volatile blowing agent are separately
Alternatively, a volatile blowing agent is contained in the polymer particles and then dispersed in a dispersion medium. At this time, if necessary, a dispersant such as finely divided aluminum oxide and titanium oxide, basic magnesium carbonate, basic zinc carbonate, carbonate is added. Cal/Lamb etc. can be used. The amount of this dispersant added is usually 0.01 to 10 parts by weight per 100 parts by weight of the polymer particles.

The dispersion medium used in the present invention may be any solvent that does not dissolve the polymer particles, such as one of water, ethylene glycol, glycerin, methanol, ethanol, etc.
Examples include species or mixtures of two or more thereof, but water is usually preferred.

In the present invention, after dispersing the polymer particles in a dispersion medium,
The temperature inside the container is expressed by the formula: Tnn +27 <, T≦TH
D +45 (where T is the temperature inside the container (C), THD
indicates the heat distortion temperature ('C) of the polymer particles. ) While maintaining the temperature within the range indicated by ), release the - end of the container.

Here, if the temperature inside the container is below Ts■D+ 27 (C), the pre-expanded particles will have low foaming and the A bubble diameter will be small, and if the temperature exceeds Th1n -+-45 (℃) In this case, only a low foaming product can be obtained and the object of the present invention cannot be achieved. In the present invention, the heat distortion temperature was determined according to ASTM D 648, and this method involves supporting both ends of a rectangular parallelepiped specimen with a length of 127+w, a width (depth) of 13 fins, and a thickness of 13 mm. With a bending stress of 4.6-- applied to the part, the temperature was raised at 2℃,
The temperature at which a deflection of 0.25 cm (depth 13 cm) occurred was determined. In addition, the heat distortion temperature of each polymer particle determined by the above method is as follows. The melting point of each particle is also listed for reference.

Polymer particles (base material) Heat deformation shield Melting point 7 Lesig North Picuri French copolymer 103℃
140°C (Ethylene J#: 4 weight skin): x, 5-V/-7'bl='1//7'M, copolymer 115°C 162°C (ethylene component:
20 weight) Propylene homopolymer 117℃ 16
5°C In the present invention, the pressure inside the container after the start of pre-foaming may be either higher than or lower than the vapor pressure of the blowing agent, but lower than the vapor pressure (Po), particularly 0.7P.

In the above case, it is preferable because the pre-expanded particles act effectively to have an appropriate cell diameter, and the atmosphere in which the polymer particles and dispersion medium are released need only be at a lower pressure than the inside of the container, and is usually a normal pressure atmosphere. is selected.

Further, in the present invention, pre-firing is carried out by discharging the mixture of polymer particles and dispersion medium into a low pressure atmosphere.
Specifically, this is carried out, for example, by passing through a discharge pipe provided at the lower end of the container.

In this case, if the discharge pipe is configured to have an air inlet in the vicinity of the container to introduce air, the pre-expanded particles can be cooled, thereby preventing over-foaming and increasing the pre-expanded particles. Open cells and deformation can be prevented, and the pre-expanded particles can be smoothly transported by preventing clogging in the discharge pipe.

The pre-expanded particles obtained by the present invention have an expansion ratio of 15 to 5.
They are particles with a high foaming rate of 0 times, and have an appropriate number of cells (appropriate cell diameter) of 300 cells/- or less.

In producing a foam molded article using the pre-expanded particles obtained by the present invention, for example, the pre-expanded particles are aged at a predetermined temperature and under normal pressure, and then, if necessary, the pre-expanded particles are aged at a predetermined temperature and under a predetermined pressure. The inorganic gas mani is aged under pressure with a mixture of inorganic gas and a volatile blowing agent to apply increased pressure inside the particles, and then the pre-expanded particles are filled into a mold for molding.
For example, steps 2 to 5 are heated and foamed using sea (G) steam.

In this way, a molded body according to the mold can be obtained.

The molded product thus obtained can be used for packaging materials, cushioning materials, vehicle width members, construction materials, food containers, heat insulating materials, flotation materials, and the like.

As explained above, the pre-expanded particles obtained by the present invention are highly foamed and have an appropriate cell diameter, so they have good moldability, and the molded products obtained using them have little shrinkage and high flexibility ( It has excellent physical properties such as strong stiffness.

Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples.

Examples 1 to 6 and Comparative Examples 1 to 4 The resin particles shown in Table 1, water, dichlorodifluoromethane, and fine particulate aluminum oxide were poured into a sealed container at the indicated mixing ratio, and the mixture was stirred. , 125-1 at the indicated pressure
After raising the temperature to 65℃ and making the resin particles contain dichlorodifluoromethane, one end of the container is opened while maintaining the temperature inside the container at the indicated temperature, and the particles and water are released into the atmosphere at the same time. and dried to obtain pre-expanded particles. Table 1 shows the expansion ratio and the number of bubbles in cross section 1 of the obtained pre-expanded particles.

Next, the pre-expanded particles were aged at room temperature and pressure for 50 hours, and then pressure-aged at 20°C and 211-degree pressure for 100 hours in a mixed gas of air and dichlorosiftetramethane, and then filled into a mold. and water vapor pressure 2.5 kQ/cd
(G) (?ndum copolymer), 5.3W-d (G)
(Pro-copolymer) was used for molding. The molded bodies obtained in each example had good moldability, little shrinkage, and high flexibility (strong stiffness), but the molded body of Comparative Example 1 had large shrinkage during molding, and compared to The molded product of Example 2 was not good, with some parts being open cells.

Procedural amendment (voluntary) 12F4, 1980 Director General of the Japan Patent Office Shima 1) Haruki Tono1, Indication of the case 1982 Patent Application No. 1759862, Name of the invention Method for producing pre-expanded polypropylene resin particles3, Relationship with the person making the amendment Patent applicant #11, 2-1 Uchisaiwai-cho, Chiyoda-ku, Tokyo Japan Styrene Paper Co., Ltd. Representative Kazuyoshi Nagano 4, Agent 2-7 Kanda Sakuma-cho, Chiyoda-ku, Tokyo 101 Japan 5. Date of pressure inspection order Voluntary amendment 6. Number of inventions increased by amendment None 7. Subject of amendment Detailed explanation of the invention in the specification column 8, @Correct content As attached 1. Page 2 of the specification On the 12th line, replace "Number of bubbles" with "
The average number of bubbles (hereinafter simply referred to as the number of bubbles) is corrected.

2. In the 3rd line of page 3 of the same @, the phrase "bubble diameter" is corrected to "average bubble diameter (hereinafter simply referred to as bubble diameter)".

3. Insert "The number of bubbles was measured by observing the cut surface with an electron microscope" after "shown in the table" on page 10, line 5.

Written amendment to the above procedure (voluntary) February 20, 1980 Haruki Shimada, Commissioner of the Japan Patent Office1, Indication of the case, Patent Application No. 175986, filed in 1982, Name of the invention, Amendment to the manufacturing method of pre-expanded polypropylene resin particles Patent applicant: 2-1-1 Uchisaiwai-cho, Chiyoda-ku, Tokyo Japan Styrene Paper Co., Ltd. Representative Kazuyoshi Nagano Representative Address: 101 & Date of amendment order Voluntary amendment & Specification subject to amendment Kusunoki 7 of Detailed Description of the Invention, ``electron microscope'' in line 5 of page 10 of the amended statement of contents is ``1 microscope.''
and correct it.

Procedural amendment (Malotaka) February 1980 1lt1 Director of the Patent Office Wakasugi Kazu Shishidono1, Incident display Relationship with the Showa S. year patent original $1117 assault case No. 98-
Patent applicant address: No. 1, Til 3, Uchinaka-cho, Chiyoda-ku, Tokyo Name: Japan Styrene Vapor Co., Ltd. 5, Date of amendment order: m1allaE1, Specification, page 11, No. 1
In the volatile blowing agent column of Example 1 in the table, "dichlorodifluoromethane (23:α09 mol) 1" is corrected to "dichlorop-difluoromethane (23:α19 mol)".

2. Resin particle column of Example 5 in Table 1, page 11 of the specification [Ethylene-propylene random copolymer (100)]
[Ethylene-propylene block copolymer (1)
00) Corrected as J.

& Specification jI page 111, Table 1, column of resin particles of Example 6 "Ethylene-propylene block copolymer (100)"
The text has been corrected to read "Pyrene homopolymer (100)".

Claims (1)

[Claims] A step of incorporating 0.08 to 0.25 mol of a volatile blowing agent into the polypropylene polymer particles per 100 parts by weight of the wrinkled polymer particles, a step of dispersing the polymer particles in a dispersion medium in a closed container, and the temperature inside the above container is expressed as: T,
+ 27 (T≦〒, +45 (where T is the temperature inside the container (
C), THJ) indicates the heat deformation temperature (℃) of the polymer particles, one end of the container is opened while maintaining the temperature in the range expressed by ), and the particles and dispersion medium are simultaneously heated inside the container under low pressure. A method for producing pre-expanded polypropylene resin particles, which comprises a step of releasing the particles into an atmosphere of