JPS59176336A - Expanded polypropylene resin particles - Google Patents

Abstract

PURPOSE:Expanded particles having an excellent in-mold moldability and capable of forming a low-density (high expansion ratio) molding of low shrinkage and water absorption, having a crystal structure which gives a DSC curve having a peak characteristic of a PP resin and a high-temperature peak of the side of a temperature higher than that of the former. CONSTITUTION:Expanded PP resin particles having a crystal structure which, when analyzed by differential scanning colorimetry, gives a DSC curve (a DSC curve obtained when 1-3mg of the expanded PP resin particles are heated to 220 deg.C on a differential scanning colorimeter at a rate of temperature increase of 10 deg.C/min) having a peak characteristic of PP resin and a high-temperature peak on the side of a temperature higher than that of the former peak, preferably by at least 5 deg.C. The resin particles have an excellent in-mold moldability. By specifying the expansion temperature at a temperature which is lower than Tm and lies between Tm-25 deg.C and Tm-5 deg.C, wherein Tm is the temperature at which melting is finished, it is possible to obtain these expanded particles having a structure which gives a DSC curve having the characteristic peak and the high- temperature peak.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to foamed polypropylene resin particles having good in-mold formability.

It is obtained by filling a cavity with pre-expanded particles and heating and foaming them. The so-called bead foam molded product (in-mold molded product) has cushioning properties,
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 polystyrene foam particles have been known as this type of molded body, but polystyrene foam molded bodies have the fatal disadvantage of being brittle and have the disadvantage of being inferior in chemical resistance. , the improvement was stopped early on. A molded body made of crosslinked polyethylene foam particles has been proposed as a solution to these drawbacks. However, in the case of crosslinked polyethylene foam particles, it is difficult to obtain a molded product with low density (high foaming) by in-mold molding.

When trying to obtain a molded product with a low density, the result was a molded product with significant shrinkage, high water absorption, and poor physical properties, making it impossible to obtain a molded product that could be used for commercial purposes. .

Therefore, the present inventors have focused on the excellent physical properties of polypropylene resin, and have conducted research on in-mold molded bodies made of expanded polypropylene resin particles in order to solve the drawbacks of conventional in-mold flooded bodies. .

However, polypropylene-based resin foam particle internal structure has a low density (high foaming) and a low water absorption rate.

Moreover, while it is possible to obtain a molded product with a low shrinkage rate and excellent dimensional stability, there are also cases where only a molded product with a high shrinkage rate can be obtained, making it difficult to obtain a stable and good molded product. It had a point.

As a result of further intensive research by the present inventors to investigate the cause of this, we found that the DSC curve obtained by measuring the differential scanning thermal deformation of polypropylene <8 resin expanded particles (pre-expanded particles) used for in-situ molding To complete the present invention, it is possible to obtain a good in-mold molded body when using polypropylene resin foam particle gold having a crystal structure in which a unique characteristic peak and a high temperature peak 1 joll higher than the characteristic peak appear. reached.

That is, the present invention provides D SC11! obtained by differential scanning thermal determination of expanded polypropylene resin particles. l line (
However, 1 to 3 mg of expanded polypropylene resin particles were heated to 220°C at a heating rate of 10°C/min using a differential scanning calorimeter.
Polypropylene resin foam characterized by having a crystal structure in which a characteristic peak specific to the polypropylene resin and a high temperature peak on the higher temperature side than the temperature of the characteristic peak appear in the DSC curve obtained when the temperature is raised to The gist is particles.

In the present invention, the polypropylene resin includes:

Propylene homopolymers, ethylene-propylene block copolymers, ethylene-propylene random copolymers, etc. are used, and ethylene-propylene random copolymers are particularly preferred.

In the present invention, the DSC curve obtained by differential scanning calorimetry of foamed polypropylene resin particles refers to a DSC curve obtained by measuring 1 to 3 mg of foamed polypropylene resin particles with a differential scanning calorimeter at 10" (220°C at a heating rate of 1:7 minutes). For example, the DSC curve obtained when the sample is heated from room temperature to 220'C at a heating rate of 10°C/min is the first DSC curve, and the second DSC curve is 40” at a cooling rate of 10°C/min from 220°C
The temperature is lowered to around C, and the temperature rises to 0 degrees Celsius 10"C at a heating rate of 7 minutes.
The DSC curve obtained when the temperature is raised to 20° C. is used as the second DSC curve, and the characteristic peak and high temperature peak can be determined from these DSC curves.

That is, the characteristic peak in the present invention is an endothermic peak unique to the polypropylene resin constituting the expanded particles, and is thought to be due to the so-called endotherm of the polypropylene resin during melting. The characteristic peak is the first DS
The C song flK also appears in the second DSC song, although the temperature at the top of the peak may be slightly different between the first and second times.

The difference is less than 5°C, usually 2°C.

On the other hand, the high temperature peak in the present invention refers to the first DS
C [higher temperature 111 than the above characteristic peak at 1 tlfl] This is an endothermic peak that appears at a high temperature of 111], and this high temperature peak does not appear in DSC track 6.Polypropylene resin foam particles have poor in-mold forming properties, and are not suitable for good forming ( It is thought that the above-mentioned high-temperature peak is not due to the existence of a crystal structure different from the structure that appears in the above-mentioned characteristic peaks, and although the high-temperature peak appears in the first DSC bending, It does not appear in the second DSC curve obtained by increasing the temperature under the same conditions.Therefore, the structure that appears as a high temperature peak is the one that the foamed polypropylene resin particles of the present invention itself had, and was determined by the differential scanning calorimeter. It was not caused by heating.

It is desirable that the difference between the temperature of the characteristic peak appearing in the second DSC curve and the temperature of the high temperature peak appearing in the first DSC curve is large, and the temperature at the peak of the characteristic peak of the second DSC curve and the high temperature are preferably large. The difference from the peak temperature is 5°C or more, preferably 10°C or more.

The foamed polypropylene resin particles of the present invention contain polypropylene resin particles in a closed container, 100 to 400 parts by weight of water per 100 parts by weight of the resin particles, and 5 to 5 parts by weight of a volatile foaming agent (for example, dichlorodifluoromethane). Weigh 30 parts by weight of 2 dispersants (for example, fine-grained aluminum oxide) and 051 to 3 parts by weight, and do not raise the temperature above the melting end temperature Tm (T
m-25°C to Tm-5°C (Tm is the melting fff end temperature of the polypropylene resin. In the present invention, Samples 6 to 8
M, 47 was heated to 220°C at a temperature increase rate of 10°C/min with a differential scanning calorimeter 1, and then moistened to around 40°C at a cooling rate of 10°C/min, and then moistened again at 10°C/min. The temperature was raised at a heating rate of 220"C at a temperature rise rate of 220"C, and the humidity at which the tail of the DSCSC curved heat peak obtained by the second temperature rise returned to the baseline at the high temperature side was determined as the melting end humidity. And so.

), one end of the container is opened and the resin particles and water are released into a lower pressure atmosphere from inside the container to foam the resin particles.

As mentioned above, during foaming, the temperature at which the foaming humidity ends is T.
By specifying the temperature within the above-mentioned constant range without increasing the temperature above m, a characteristic peak and a high-temperature peak appear in the DSCIItl line.

Expanded particles of the present invention can be obtained. If the foaming temperature is out of the above range, or even if it is within the above range, once the temperature is raised above the melting end mixture Tm, only the characteristic peak will appear in the DSC curve section of the obtained expanded particles, and the high temperature peak will not appear. Doesn't appear.

Hereinafter, the present invention will be explained in more detail by giving Examples 19 and Comparative Examples.

Examples 1 to 3 and Comparative Examples 1 to 3 300 g of water and 100 g of ethylene-propylene random copolymer particles (Tm = 153°C) in a closed container.

03 g of ultrafine aluminum oxide (dispersant) and the volatile blowing agent shown in Table 1 were blended and heated while stirring. After maintaining the foaming temperature shown in Table 1 for 30 minutes, one end of the container was opened while the pressure inside the container was maintained at 3oky/cflCG) with nitrogen gas, and the resin particles and water were released into the atmosphere at the same time. Then, the resin particles were foamed to obtain foamed particles. Table 1 shows the apparent (bulk) expansion ratio of the obtained expanded particles. Next, each of the foamed particles obtained was heated to 220°Ct at a heating rate of 10°C/min using a differential scanning calorimeter (manufactured by Takasu Seisakusho, Model T-30) for the first measurement. After that, the temperature was lowered to 40°C at a rate of 10°C and 7' minutes, and the temperature was increased to 220°C at a rate of 0°C/min for a second measurement. Among the DSC curves of the expanded particles of Examples 1 to 3, the DSC1111 curve of the expanded particles of Example 1 is shown in FIG. In addition, regarding the comparative example, DSCIflli? of the foamed particles of comparative example 3? I is shown in FIG. Figures 1 and 2
In the figure, the solid line is the DS obtained in the first 6111 constant.
C[1IIIil is shown, and the one dotted line shows the DSC@ line obtained in the second measurement. DSC obtained for the foamed particles of Examples 1 to 3
Find the difference (ΔT) between the temperature at the top of the high temperature peak (bl) appearing on the SCIIil line.

It is also shown in Table 1. Next, Examples 1 to 3 and Comparative Example 1
~3 each foamed particle 'e 2 kg / cd (c) of air for 24 hours and then 50 mm x 300 m 1 x 3
Fill a mold with internal dimensions between 0.00 and 0.00.

3.Heat with steam of 2 kfi / crl (G) 2
Foam molding was performed. Table 1 shows the results of each of the obtained bodies in an open air at 80°C.

As explained above, the expanded polypropylene resin particles of the present invention have a crystal structure in which a characteristic peak specific to the polypropylene resin and a high temperature peak on the higher temperature side of the characteristic peak appear in the DSC curve. is DS
The molded product does not shrink significantly unlike in-mold molded products using expanded polypropylene resin particles that do not appear on the C curve.

Excellent in-mold moldability when foamed particles are molded in a mold.

In addition to obtaining a molded product with low density (high foaming),
The molded product obtained has a low shrinkage rate and low water absorption rate.

Has excellent physical properties. In addition, the in-mold molded body made of expanded polypropylene resin particles does not have the disadvantage of being brittle like the in-mold molded body made of expanded polystyrene resin particles, and can provide a molded body with excellent rain impact resistance and chemical resistance. In addition, it has various effects such as being able to provide an excellent molded product with low shrinkage and water absorption even when the density is lower (highly foamed) than in-mold molded products made of crosslinked polyethylene foam particles.

[Brief explanation of drawings]

The drawings show DSC curves obtained by differential scanning calorimetry.
The figure is a DSC curve of Comparative Example 30 expanded particles. (1 procedural amendment) August 22, 1980 Commissioner of the Japan Patent Office Kazuo Wakasugi 1, Indication of the case Patent Application No. 50048 of 1988 2゜ Title of the invention Polypropylene resin foam particles 3,
Relationship with the case of the person making the amendment Patent applicant 5, Date of amendment order Voluntary amendment 6, Number of inventions increased by the amendment L7, Detailed explanation of the invention in the specification to be amended. (1) “High 31!+” beak on page 3, line 14 of the specification
is corrected as "high temperature peak". (2) "*2: JIS
Measured by -6767B method. "r JIS
- It was measured by the 6767B method. ” he corrected. The above amendment was filed on November 26, 1980, by Mr. Kazuo Wakasugi, Commissioner of the Japan Patent Office, ■, Description of the matter, Patent Application No. 50048 of 1982, 2, Title of the invention: Polypropylene resin foam particles 3, Person making the amendment Relationship to the case Patent applicant address 2-1-1-5 Uchisaiwai-cho, Chiyoda-ku, Tokyo Date of amendment order Voluntary amendment 8, Contents of amendment
Attached document 〇(1) “It was done” on page 6, line 5 of the specification.
Correct it with "That's what I used to do." (2) Delete the phrase "This was not caused by heating using a differential scanning calorimeter" in lines 5 and 6 of page 6. [o, 3gJ in the 6th line is corrected to "0.3 part by weight". (4) In the foaming conditions section of Table 1 on page 10, in the volatile blowing agent section, "181/J" in the column of Example 1 was replaced with "181/J".
"parts by weight", r20Ji'J in the column of Example 2 is "20 parts by weight", and "xzlJ" in the column of Example 3 is "11 parts by weight".
, r13.9J as "13 parts by weight" and "13 parts by weight" in the column of Comparative Example 1.
8g" to "8 parts by weight" and "ao,!i" in the column of Comparative Example 2.
lJ is "30 parts by weight" and r16,9J in the column of Comparative Example 3
are respectively corrected to "16 parts by weight". that's all

Claims (1)

[Scope of Claims] (11 DSC [l1lil] obtained by a differential scanning calorimeter of foamed polypropylene resin particles (1 to 3 mg of the foamed polypropylene resin particles was measured by a differential scanning calorimeter at a heating rate of 10°C/min) A polypropylene characterized by having a crystal structure in which a characteristic peak specific to the polypropylene resin and a high temperature peak on the higher temperature side than the temperature of the characteristic peak appear in the DSC curve obtained when the temperature is raised to 220 ° C. (2) The polypropylene resin according to claim 1-1, wherein the difference between the temperature at the peak of the characteristic peak and the temperature at the peak of the high-temperature peak is 5° C. or more. Resin foam particles.