JP2003171516A - Expandable polypropylene-based resin composition and pre-expanded particle composed thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide polypropylene-based resin pre-expanded particles which are used in producing in-mold foam-molded articles of a polypropylene-based resin having reduced discoloration and reduced weight variability and have smaller variations in the cell diameter and the expansion ratio than the conventional ones. <P>SOLUTION: The pre-expanded particles are produced by using an expandable polypropylene-based resin composition composed of (A) a polypropylene-based resin, (B) a hydrophilic polymer, and (C) a compound having a triazine skeleton and a molecular weight of ≤300 based on a unit triazine skeleton. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyolefin resin which can be suitably used for producing an in-mold foam molded article of polypropylene resin used for cushion packaging materials, box casings, heat insulating materials, automobile bumper core materials and the like. The present invention relates to pre-expanded particles and an expandable polyolefin-based resin composition used therein.

[0002]

2. Description of the Related Art Conventionally, polypropylene resin particles are dispersed in a water-based dispersion medium together with a foaming agent and heated to a constant pressure.
A method is known in which a polyolefin-based resin particle is impregnated with a foaming agent at a constant temperature and then discharged under a low pressure atmosphere to obtain pre-expanded particles. As a foaming agent, propane,
A method using a volatile organic blowing agent such as butane (for example, Japanese Patent Publication No. 56-1344), carbon dioxide gas, nitrogen,
A method using an inorganic gas such as air (for example, Japanese Patent Publication No. 4-
Japanese Patent No. 64332 and Japanese Patent Publication No. 4-64334) are disclosed.

However, volatile organic blowing agents are expensive and costly. Further, volatile organic foaming agents such as propane and butane have the effect of plasticizing the polyolefin resin, and while it is easy to obtain a high expansion ratio, on the other hand, due to the plasticizing effect, the expansion ratio of the pre-expanded particles and the crystalline state It has the drawback of being difficult to control.

When an inorganic gas such as carbon dioxide, nitrogen, or air is used, the impregnation ability into the polyolefin resin is low, so that it is generally necessary to impregnate it at a high pressure of about 3 to 6 MPa. For this reason, the impregnation tank for impregnating the foaming agent into the polyolefin-based resin requires high pressure resistance performance, which has a drawback of increasing equipment cost.

As a method for solving these drawbacks and economically producing pre-expanded polyolefin resin particles which can be suitably used for producing an in-mold foam molded article, a hydrophilic compound is contained in the polyolefin resin. According to the method, water used as a dispersion medium is used as a foaming agent (for example, JP-A-10-306179 and JP-A-11-10657).
No. 6) is proposed.

[0006]

However, regarding the expansion ratio variation and the cell diameter variation, the required level is higher than ever, and water is used as a foaming agent to produce the polyolefin resin pre-expanded particles. In the method as well, there are cases where variations in foaming ratio and variations in cell diameter do not reach required levels, and further improvements are required.

If the expansion ratio is large, the problem of large variation in the weight of the in-mold foamed product occurs. In recent years, product quality standards have become stricter,
In order to reduce the number of man-hours for inspecting the in-mold foam molded article, there is a demand for pre-expanded particles having a smaller expansion ratio variation than ever before.

Further, if there is a variation in cell diameter, color unevenness occurs and the appearance is impaired, so further improvement is required.
In the case of an in-mold foam molded article colored by containing a pigment or a dye, in particular, in the case of an in-mold foam molded article colored in black, color unevenness is more noticeable than that of an uncolored white in-mold foam molded article. There is a strong demand for improvement in diameter variation.

[0009]

As a result of earnest research, the present inventors have found that a triazine skeleton specific to an expandable polypropylene resin composition comprising a conventionally known polypropylene resin, a hydrophilic polymer and an inorganic filler. It was found that the above-mentioned problems can be solved by containing a compound having the present invention, and the present invention has been completed.

That is, the present invention is characterized by comprising (A) a polypropylene resin, (B) a hydrophilic polymer, and (C) a triazine skeleton, and having a molecular weight per unit triazine skeleton of 300 or less. And a foamable polypropylene resin composition.

In a preferred embodiment, the expandable polypropylene resin composition described above is characterized by containing (B) a hydrophilic polymer in an amount of 0.01 to 20 parts by weight.

In a more preferred embodiment, the compound (C) has a triazine skeleton and contains 0.05 to 5 parts by weight of a compound having a molecular weight of 300 or less per unit triazine skeleton. It relates to the expandable polypropylene resin composition described.

A further embodiment relates to the expandable polypropylene resin composition according to any one of the above items, which comprises (D) an inorganic filler.

As a further embodiment, the expandable polypropylene resin composition according to any one of the above items is characterized in that (D) the inorganic filler is contained in an amount of 0.005 to 10 parts by weight.

In a further preferred embodiment, the polypropylene resin is one selected from the group consisting of ethylene-propylene random copolymer, propylene-butene-1 random copolymer and ethylene-propylene-butene-1 random copolymer. Alternatively, it relates to the expandable polypropylene-based resin composition according to any one of the above items, which is a mixture.

[0016] In a further preferred embodiment, the expandable polypropylene according to any one of the preceding items, wherein the hydrophilic polymer is an ethylene-based ionomer resin obtained by crosslinking an ethylene- (meth) acrylic acid copolymer with an alkali metal ion. A resin composition.

In a further preferred embodiment, the compound having a triazine skeleton and having a molecular weight of 300 or less per unit triazine skeleton is one or a mixture selected from the group of melamine, isocyanuric acid and melamine-isocyanuric acid condensate. The expandable polypropylene-based resin composition according to any one of the above.

A further preferred embodiment relates to polypropylene resin pre-expanded particles, characterized in that the polypropylene resin composition according to any one of the above items is used as a base resin.

A more preferred embodiment relates to the polypropylene resin pre-expanded particles described above having two melting peaks in the DSC curve obtained by differential scanning calorimetry.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION The expandable polypropylene resin composition of the present invention includes (A) polypropylene resin and (B)
A hydrophilic polymer and a compound having a (C) triazine skeleton and having a molecular weight of 300 or less per unit triazine skeleton are included.

As the polypropylene resin (A) used in the present invention, propylene homopolymer, α-olefin-propylene random copolymer, α-olefin-
Examples include propylene block copolymers. These may be used alone or in combination of two or more. In particular, ethylene-propylene random copolymers, ethylene-propylene-butene-1 random copolymers, and propylene-butene-1 random copolymers have good foaming properties and can be suitably used.

The polypropylene resin is excellent in foamability and moldability, and has a high mechanical strength when formed into an in-mold foam molded product.
In order to obtain pre-expanded particles having excellent heat resistance, the melting point is usually preferably 130 to 165 ° C, more preferably 135 ° C to 155 ° C, and the melt index (hereinafter, MI value).
Is usually 0.5 to 30 g / 10 minutes, and further 2 to 20 g
/ 10 minutes is preferable.

When the melting point is less than 130 ° C., heat resistance,
Mechanical strength tends to be insufficient. Also, the melting point is 16
If it exceeds 5 ° C, it tends to be difficult to secure fusion during in-mold foam molding. The MI value is 0.5 g / 1
If it is less than 0 minutes, it is difficult to obtain pre-expanded particles having a high expansion ratio, and if it exceeds 30 g / 10 minutes, the cells are likely to break and the pre-expanded particles tend to have a high open cell rate.

Here, the melting point means that 1 to 10 mg of polypropylene resin is heated from 40 ° C. to 220 ° C. at a rate of 10 ° C./minute by a differential scanning calorimeter, and then 40 ° C.
Cooling at a rate of 10 ° C / min until 220 ° C again at 10
The peak temperature of the endothermic peak in the DSC curve obtained when the temperature is raised at a rate of ° C / min. Further, the MI value is a value measured according to JIS K7210 at a temperature of 230 ° C. and a load of 2.16 Kg.

The hydrophilic polymer (B) used in the present invention includes ethylene-acrylic acid-maleic anhydride terpolymer, ethylene- (meth) acrylic acid copolymer, ethylene- (meth) acrylic acid copolymer. Carboxyl group-containing polymers such as ionomer resins obtained by cross-linking coalesced with metal ions; polyamides such as nylon 6, nylon 6,6 and copolymerized nylon; thermoplastic polyester systems such as block copolymers of polybutylene terephthalate and polytetramethylene glycol Examples thereof include elastomers. These may be used alone or in combination of two or more.
In particular, an ethylene-based ionomer resin obtained by cross-linking an ethylene- (meth) acrylic acid copolymer with an alkali metal ion such as sodium ion or potassium ion is preferable because it gives a good water content and a good foaming property. Furthermore, an ethylene-based ionomer resin obtained by crosslinking an ethylene- (meth) acrylic acid copolymer with potassium ions gives a larger average cell diameter, and is therefore more preferable.

The amount of the hydrophilic polymer used is not particularly limited depending on the kind of the hydrophilic polymer, but usually, the upper limit of the amount used is preferably 20 parts by weight, based on 100 parts by weight of the polypropylene resin. More preferably parts by weight. On the other hand, the lower limit of the amount used is preferably 0.01 parts by weight,
0.1 parts by weight is more preferable. More preferably, the upper limit of the amount used is 5 parts by weight and the lower limit of the amount used is 0.3 part by weight. If it is less than 0.01 part by weight, it is difficult to obtain pre-expanded particles having a high expansion ratio. If it exceeds 20 parts by weight, the heat resistance and mechanical strength tend to be greatly reduced.

In the present invention, a compound having a (C) triazine skeleton and having a molecular weight per unit triazine skeleton of 300 or less is used. Here, the molecular weight per unit triazine skeleton is a value obtained by dividing the molecular weight by the number of triazine skeletons contained in one molecule. If the molecular weight per unit triazine skeleton exceeds 300, the effect of suppressing the variation in foaming ratio and the variation in cell diameter tends to be insufficiently exhibited. Examples of the compound (C) having a triazine skeleton and having a molecular weight of 300 or less per unit triazine skeleton used in the present invention include melamine (chemical name: 1,3,5-triazine-2,4,6-triamine), Ammeline (1, 3, 3)
5-triazine-2-hydroxy-4,6-diamine), ammelide (the same 1,3,5-triazine-2,4)
-Hydroxy-6-amine), cyanuric acid (the same 1, 3,
5-triazine-2,4,6-triol), isocyanuric acid (the same 1,3,5-triazine-2,4,6 (1)
H, 3H, 5H) -trione), acetoguanamine (the same 1,3,5-triazine-2,6-diamine-4-methyl), benzoguanamine (the same 1,3,5-triazine-).
2,6-diamine-4-phenyl), tris (methyl)
Isocyanurate, tris (ethyl) isocyanurate, tris (butyl) isocyanurate, tris (2-
Examples thereof include hydroxyethyl) isocyanurate and melamine / isocyanuric acid condensates. These may be used alone or in combination of two or more. In particular, melamine, isocyanuric acid, and melamine-isocyanuric acid condensate, which are highly effective in suppressing the variation in foaming ratio and the variation in cell diameter, can be preferably used.

The compounds having these triazine skeletons and having a molecular weight of 300 or less per unit triazine skeleton usually have an average particle diameter of 0.1 to 800 μm, and further 1 to 1 in order to obtain a more uniform and good cell structure. It is preferably 100 μm, and the more uniform the particle diameter is, the more preferable. Further, a metal soap such as magnesium stearate, barium stearate or calcium stearate may be added in an amount of 0.1 to 1% to prevent caking.

Further, the compound having the triazine skeleton and having a molecular weight of 300 or less per unit triazine skeleton is more preferably present as particles at the processing temperature when the polypropylene resin composition is prepared. When it has a melting point, it preferably has a melting point of 180 ° C. or higher. In the case of decomposing without having a melting point, one having a decomposition temperature of 230 ° C or higher is preferable.

The amount of the compound having the triazine skeleton and having a molecular weight of 300 or less per unit triazine skeleton is not particularly limited, but the upper limit of the amount used is usually 5 parts by weight per 100 parts by weight of the polypropylene resin. Parts is preferred, and 3 parts by weight is more preferred. On the other hand, the lower limit of the amount used is preferably 0.05 parts by weight, more preferably 0.1 parts by weight. If the amount is less than 0.05 part by weight, the effect of suppressing the variation in foaming ratio and the variation in cell diameter may not be sufficiently exhibited. If it exceeds 5 parts by weight, the cell diameter becomes finer and the open cell ratio increases, tending to deteriorate the moldability.

Examples of the inorganic filler (D) used in the present invention include clay such as talc, mica, kaolin, montmorillonite, bentonite, attapulgite, laponite and sepiolite, natural or synthetic silica, natural or synthetic calcium carbonate, titanium oxide, oxide. Examples include zinc. These may be used alone or in combination of two or more. In particular, talc having an average particle size of 1 to 20 μm,
Mica having an average particle size of 1 to 20 μm, average particle size of 0.1 to 10
μm swelling mica, kaolin having an average particle size of 0.1 to 10 μm, wet synthetic silica having an average particle size of 0.1 to 10 μm and its surface modified product, average particle size of 0.001 to 0.05 μm
Dry-synthesized silica and its surface-modified product, average particle size 0.
05-0.5 μm light calcium carbonate and its surface modified product, purified bentonite with an average particle size of 1-20 μm, attapulgite with an average particle size of 0.05-0.5 μm, and laponite with an average particle size of 10-200 μm are good. A cell structure is provided and can be preferably used.

The above-mentioned inorganic filler functions as a cell nucleating agent,
Although it does not necessarily have to be used because it has a function of helping to form uniform cells, it improves the foamability, that is, it facilitates obtaining pre-expanded particles having a high expansion ratio. The amount used is not particularly limited,
The upper limit of the amount used is preferably 10 parts by weight and more preferably 5 parts by weight with respect to 100 parts by weight of the polypropylene resin. On the other hand, the lower limit is preferably 0.005 parts by weight, and 0.0
1 part by weight is more preferred. If it exceeds 10 parts by weight, the mechanical strength and impact resistance of the pre-expanded particles when formed into an in-mold expanded molded article tend to be poor.

(A) polypropylene resin of the present invention,
(B) a hydrophilic polymer, (C) having a triazine skeleton,
The expandable polyolefin resin composition comprising a compound having a molecular weight per unit triazine skeleton of 300 or less and (D) an inorganic filler optionally contained is usually melted using an extruder, a kneader, a Banbury mixer, a roll or the like. However, it has a desired particle shape such as a cylindrical shape, an elliptic cylinder shape, a spherical shape, a cubic shape, or a rectangular parallelepiped shape, and the particle weight of the particles is 0.2 to
Processed to 10 mg, preferably 0.5-6 mg of resin particles. At this time, if necessary, an additive such as a coloring agent such as carbon black, an antistatic agent, a flame retardant, an antioxidant, a weathering agent or the like can be added.

In the production of the pre-expanded particles in the present invention,
Conventional methods can be used. For example, in a closed container, an aqueous dispersion medium containing the resin particles, a dispersant and a dispersion aid is charged, the temperature is raised with stirring to make the resin particles contain water at a constant temperature, and an inorganic gas such as nitrogen or air (carbon dioxide) is added. 2-10 after holding at a constant pressure (excluding gas)
The pre-expanded particles are produced by a method of discharging under a pressure lower than the internal pressure of the closed container through an opening orifice of mmφ. The low-pressure atmosphere is preferably kept at a high temperature in order to further increase the expansion ratio, and particularly preferably kept at 90 to 100 ° C. by steam.
The closed container to be used is not particularly limited as long as it can withstand the container internal pressure and the container internal temperature at the time of pre-foaming production, and for example, an autoclave type pressure resistant container can be mentioned.

As the dispersant, for example, a slightly water-soluble inorganic compound such as basic tribasic calcium phosphate, basic magnesium carbonate, calcium carbonate and the like, and as the dispersing aid, for example, sodium dodecylbenzene sulfonate, n-paraffin sodium sulfonate, wrinkle olefin sulfone. Anionic surfactants such as acid soda are used. Of these, the use of basic tribasic calcium phosphate and sodium n-paraffin sulfonate is preferable for obtaining good dispersibility. The amount of these dispersants and dispersion aids used varies depending on the type and the type and amount of the polypropylene-based resin used.
0.1 to 3 parts by weight of the dispersant and 0.0001 to 0.1 part by weight of the dispersion aid with respect to 00 parts by weight.

In order to improve the dispersibility of the resin particles in water, it is usually preferable to use 20 to 100 parts by weight of the resin particles with respect to 100 parts by weight of water.

The pre-expanded particles thus obtained preferably have two melting peaks in the DSC curve obtained by differential scanning calorimetry. In the case of pre-expanded particles having two melting peaks, the in-mold foam moldability is good,
It is possible to obtain an in-mold foam molded article having good mechanical strength and heat resistance.

Here, the DSC curve obtained by the differential scanning calorimetry of the pre-expanded particles means the pre-expanded particles 1 to 1
DS obtained when 0 mg was heated from 40 ° C to 220 ° C at a heating rate of 10 ° C / min by a differential scanning calorimeter
It is a C curve.

The pre-expanded particles having two melting peaks as described above can be easily obtained by setting the temperature in the container during pre-expansion to an appropriate value. Usually, the temperature in the container is equal to or higher than the melting point of the polypropylene-based resin which is the main component of the expandable polypropylene-based resin composition, preferably the melting point +5.
℃ or more, less than melting end temperature, preferably melting end temperature-
It is selected from temperatures of 2 ° C or lower.

The term "melting end temperature" used herein means 4 to 10 mg of polypropylene resin by a differential scanning calorimeter.
The temperature is raised from 0 ° C to 220 ° C at a rate of 10 ° C / min, then cooled to 40 ° C at a rate of 10 ° C / min, and again 220 ° C.
It is the temperature at which the tail of the melting peak of the DSC curve obtained when the temperature was raised up to 10 ° C./min returned to the baseline position on the high temperature side.

The pre-expanded particles obtained as described above can be formed into an in-mold expanded molded article by a method known in the art. For example, (a) a method in which pre-expanded particles are pressure-treated with an inorganic gas to impregnate the particles with the inorganic gas to give a predetermined internal pressure to the particles, and then the particles are filled in a mold and heat-sealed with steam or the like. A method of compressing pre-expanded particles with gas pressure and filling them in a mold and heating and fusing them with steam, etc. by utilizing the resilience of the particles. C) Filling the mold without any pre-treatment and using steam etc. A method such as heat fusion may be used.

In a preferred embodiment of the present invention,
(A) Melting point is 130 to 165 ° C., MI value is 0.5 to 30
100 parts by weight of polypropylene resin (melting point Tm ° C., melting end temperature Te ° C.) of g / 10 min, (B) Ethylene ionomer resin ion-crosslinked with ethylene- (meth) acrylic acid copolymer as a hydrophilic polymer. 01 to 20 parts by weight, (C) a compound having a triazine skeleton and having a molecular weight per unit triazine skeleton of 300 or less, isocyanuric acid, melamine or isocyanuric acid / melamine condensate 0.05 to 5 parts by weight, (D) inorganic As a filler, 0 to 10 parts by weight of talc is mixed, extruded in a strand form from an extruder, and after cooling, the strand is cut into 1 to 5 mg of cylindrical resin particles. At this time, the (B) hydrophilic polymer, (C) compound having a triazine skeleton and having a molecular weight per unit triazine skeleton of 300 or less, and (D) the inorganic filler are added in a masterbatch prepared in advance. preferable. This resin particle 10 is put in an autoclave type pressure resistant container.
100 parts by weight to 500 parts by weight of water, 0.1 to 15 parts by weight of basic tribasic calcium phosphate as a dispersant, and 0.000 parts of n-paraffin sodium sulfonate as a dispersant.
01-0.5 parts by weight was charged, the temperature was raised to a constant temperature of Tm to Te ° C., a constant pressure of 1 to 3 MPa was applied by air, and then 90 to 100 ° C. was passed through an opening orifice of 2 to 10 mmφ. A method of releasing the particles into a steam atmosphere to obtain pre-expanded particles can be mentioned.

[0043]

EXAMPLES Next, the present invention will be explained based on Examples and Comparative Examples, but the present invention is not limited to these Examples. Table 1 shows the composition of the polypropylene resin compositions of Examples 1 to 12, and Table 5 shows the foaming conditions and the physical properties of the obtained pre-expanded particles. Table 2 shows the composition of the polypropylene resin compositions of Examples 13 to 24, and Table 6 shows the foaming conditions and the physical properties of the obtained pre-expanded particles. Table 3 shows the composition of the polypropylene resin compositions of Examples 25 to 34, and Table 7 shows the foaming conditions and the physical properties of the obtained pre-expanded particles. Comparative Example 1
Table 4 shows the composition of the polypropylene resin composition of No. 9, and Table 8 shows the foaming conditions and the physical properties of the obtained pre-expanded particles.

Example 1 Ethylene-propylene random copolymer (melting point 146 ° C., melting end temperature 160 ° C., M
(I value 9 g / 10 minutes) 100 parts by weight, ethylene-based ionomer resin (trade name: Himilan SD100, manufactured by Mitsui DuPont Polychemical Co., Ltd.) obtained by potassium ion-crosslinking ethylene- (meth) acrylic acid copolymer as a hydrophilic polymer.
2 parts by weight, a compound having a triazine skeleton and having a molecular weight of 300 or less per unit triazine skeleton, 1 part by weight of isocyanuric acid (trade name Neochlor cyanuric acid P manufactured by Shikoku Chemical Industry Co., Ltd.), carbon black 2.6 as a colorant.
1. Parts by weight are melt-kneaded with a 50 mmφ single screw extruder, and the diameter is 2.
It was extruded in a strand shape from a 2 mmφ cylindrical die, cooled with water, and then cut with a cutter to obtain 1.8 mg / grain of resin particles. 100 parts by weight (65 kg) of the obtained resin particles, 2 parts of water
00 parts by weight, 0.5 parts by weight of basic tribasic calcium phosphate, 0.01 parts by weight of n-paraffin sodium sulfonate were charged into an autoclave having a volume of 0.35 m ³ , and the contents of the autoclave were stirred and the contents of the container shown in Table 5 were used. Heated to internal temperature. Then, the internal pressure of the autoclave was increased to the internal pressure of the container shown in Table 5 with compressed air, and the internal temperature of the container was maintained for 30 minutes, and then the valve at the bottom of the autoclave was opened.
The autoclave contents were discharged through a 3.2 mmφ opening orifice in a vapor saturated atmosphere at 100 ° C. to obtain pre-expanded particles. As the physical properties of the obtained pre-expanded particles,
The expansion ratio, the number of melting peaks in the DSC curve in differential scanning calorimetry, the open cell ratio, the average cell diameter, the cell diameter variation, and the expansion rate variation were measured. The results are shown in Table 5.

(Example 2) Ethylene-propylene random copolymer (melting point 146 ° C, melting end temperature 160 ° C, M
(I value 9 g / 10 minutes) 100 parts by weight, ethylene-based ionomer resin (trade name: Himilan SD100, manufactured by Mitsui DuPont Polychemical Co., Ltd.) obtained by potassium ion-crosslinking ethylene- (meth) acrylic acid copolymer as a hydrophilic polymer.
2 parts by weight, 1 part by weight of isocyanuric acid having a triazine skeleton and a molecular weight per unit triazine skeleton of 300 or less (trade name Neochlor cyanuric acid P manufactured by Shikoku Chemical Industry Co., Ltd.), talc as an inorganic filler (average particle size 8 μm) ) 0.1
5 parts by weight and 2.6 parts by weight of carbon black as a colorant are melt-kneaded with a 50 mmφ single screw extruder to obtain a diameter of 2.2 mm.
It was extruded in a strand form from a φ cylindrical die, cooled with water, and cut with a cutter to obtain 1.8 mg / grain of resin particles. Pre-expanded particles were obtained in the same manner as in Example 1, and the physical properties were measured. The results are shown in Table 5.

(Examples 3 to 7) Addition amount of ethylene ionomer resin (trade name: Himilan SD100, manufactured by Mitsui DuPont Polychemical Co., Ltd.) obtained by cross-linking an ethylene- (meth) acrylic acid copolymer with potassium ions, isocyanuric acid (trade name) Resin particles and pre-expanded particles were prepared in the same manner as in Example 2 except that the addition amount of neochlor cyanuric acid P manufactured by Shikoku Kasei Kogyo Co., Ltd. and the addition amount of talc (average particle size 8 μm) were changed to those shown in Table 1. After that, the physical properties were measured. The results are shown in Table 5.

Example 8 Resin particles and pre-expanded particles were obtained in the same manner as in Example 2 except that mica (average particle size 8 μm) was used as the inorganic filler, and the physical properties were measured. The results are shown in Table 5.

Example 9 Resin particles and pre-expanded particles were obtained in the same manner as in Example 2 except that kaolin (average particle size 0.4 μm) was used as the inorganic filler, and the physical properties were measured. The results are shown in Table 5.

Example 10 Resin particles and pre-expanded particles were obtained in the same manner as in Example 2 except that refined bentonite (trade name: BEN-GEL-23, manufactured by Hojun Mining Co., Ltd.) was used as the inorganic filler. Physical properties were measured. The results are shown in Table 5.

Example 11 Laponite as an inorganic filler (trade name: Laponite XLG manufactured by Nippon Silica Industry Co., Ltd.)
Resin particles and pre-expanded particles were obtained in the same manner as in Example 2 except that was used to measure the physical properties. The results are shown in Table 5.

(Example 12) Resin particles and pre-expanded particles were obtained in the same manner as in Example 2 except that silica (trade name: NIPGEL AZ-204 manufactured by Nippon Silica Industry Co., Ltd.) was used as an inorganic filler, and the physical properties were obtained. The measurement was performed. The results are shown in Table 5.

Example 13 Resin particles and pre-expanded particles were obtained in the same manner as in Example 2 except that light calcium carbonate (trade name: Brilliant-1500 manufactured by Shiraishi Kogyo Co., Ltd.) was used as an inorganic filler, and physical properties were obtained. The measurement was performed.
The results are shown in Table 6.

Examples 14 to 16 Ethylene ionomer resin obtained by crosslinking ethylene- (meth) acrylic acid copolymer as a hydrophilic polymer with sodium ion (trade name: Himilan 1707, manufactured by Mitsui DuPont Polychemical Co., Ltd.)
Resin particles and pre-expanded particles were obtained in the same manner as in Example 2 except that the addition amount shown in Table 2 was used, and the physical properties were measured. The results are shown in Table 6.

(Example 17) Resin particles were prepared in the same manner as in Example 1 except that melamine (trade name: Melamine BASF) was used as a compound having a triazine skeleton and a molecular weight per unit triazine skeleton of 300 or less. Then, the pre-expanded particles were obtained and the physical properties were measured. The results are shown in Table 6.

Example 18 Resin particles were prepared in the same manner as in Example 2 except that melamine (trade name, manufactured by Melamine BASF) was used as a compound having a triazine skeleton and having a molecular weight per unit triazine skeleton of 300 or less. Then, the pre-expanded particles were obtained and the physical properties were measured. The results are shown in Table 6.

(Examples 19 to 28) Ethylene- (meth)
The addition amount of ethylene ionomer resin (trade name: Himilan SD100, manufactured by Mitsui DuPont Polychemical Co., Ltd.) obtained by crosslinking an acrylic acid copolymer with potassium ions, and the amount of melamine (trade name, manufactured by Melamine BASF Co., Ltd.) are shown in Table 2 and Table 3. Resin particles and pre-expanded particles were obtained and physical properties were measured by the same method as in Example 18 except that the amount was changed. The results are shown in Tables 6 and 7.

(Example 29) Example 29 except that an ethylene ionomer resin (trade name: Himilan 1707, manufactured by Mitsui DuPont Polychemical Co., Ltd.) obtained by crosslinking an ethylene- (meth) acrylic acid copolymer with sodium ions was used as the hydrophilic polymer. Resin particles and pre-expanded particles were obtained in the same manner as in 18, and the physical properties were measured. The results are shown in Table 7.

(Example 30) Propylene-butene-1 random copolymer (melting point 14
Resin particles and pre-expanded particles were obtained in the same manner as in Example 18 except that the temperature was 8 ° C., the melting end temperature was 161 ° C., and the MI value was 8 g / 10 minutes. The results are shown in Table 7.

(Example 31) Ethylene-propylene-butene-1 random copolymer as polypropylene resin (melting point 148 ° C, melting end temperature 161 ° C, MI value 8 g /
Resin particles and pre-expanded particles were obtained in the same manner as in Example 18 except that 10 minutes) was used, and the physical properties were measured. The results are shown in Table 7.

(Example 32) Resin particles and pre-foaming were carried out in the same manner as in Example 18 except that a melamine-isocyanuric acid condensate having a triazine skeleton and a molecular weight per unit triazine skeleton of 300 or less was used. The particles were obtained and the physical properties were measured. The results are shown in Table 7.

Example 33 Isocyanuric acid (trade name Neochlor cyanuric acid P manufactured by Shikoku Chemical Industry Co., Ltd.) as a compound having a triazine skeleton and having a molecular weight per unit triazine skeleton of 300 or less is shown in Table 3. Resin particles and pre-expanded particles were obtained and the physical properties were measured by the same method as in Example 2 except that the above was used. The results are shown in Table 7.

(Example 34) Example 34 except that melamine (trade name, melamine manufactured by BASF) was used as a compound having a triazine skeleton and a molecular weight per unit triazine skeleton of 300 or less in the addition amount shown in Table 3 Resin particles and pre-expanded particles were obtained in the same manner as in 2, and the physical properties were measured. The results are shown in Table 7.

Comparative Example 1 Ethylene-propylene random copolymer (melting point 146 ° C., melting end temperature 160 ° C., M
(I value 9 g / 10 minutes) 100 parts by weight, ethylene-based ionomer resin (trade name: Himilan SD100, manufactured by Mitsui DuPont Polychemical Co., Ltd.) obtained by potassium ion-crosslinking ethylene- (meth) acrylic acid copolymer as a hydrophilic polymer.
2 parts by weight, talc as inorganic filler (average particle size 8 μm)
0.15 parts by weight, carbon black 2.6 parts by weight 50 parts
The mixture was melt-kneaded with a mmφ single-screw extruder, extruded in a strand form from a cylindrical die having a diameter of 2.2 mmφ, cooled with water, and then cut with a cutter to obtain 1.8 mg / grain of resin particles.

By the same method as in Example 1, prefoamed particles were obtained under the foaming conditions shown in Table 8 and the physical properties were measured. The results are shown in Table 8.

Comparative Example 2 Resin particles and pre-expanded particles were obtained in the same manner as in Comparative Example 1 except that mica (average particle size 8 μm) was used as the inorganic filler, and the physical properties were measured. The results are shown in Table 8.

Comparative Example 3 Resin particles and pre-expanded particles were obtained in the same manner as in Comparative Example 1 except that kaolin (average particle size 0.4 μm) was used as the inorganic filler, and the physical properties were measured. The results are shown in Table 8.

(Comparative Example 4) Resin particles and pre-expanded particles were obtained in the same manner as in Comparative Example 1 except that purified bentonite (trade name: BEN-GEL-23 manufactured by Hojun Mining Co., Ltd.) was used as the inorganic filler. Physical properties were measured. The results are shown in Table 8.

Comparative Example 5 Comparative Example 1 except that an ethylene ionomer resin (trade name: Himilan 1707, manufactured by Mitsui DuPont Polychemical Co., Ltd.) obtained by crosslinking an ethylene- (meth) acrylic acid copolymer with sodium ions was used as the hydrophilic polymer. Resin particles and pre-expanded particles were obtained in the same manner as in 1. and the physical properties were measured. The results are shown in Table 8.

(Comparative Example 6) A propylene-butene-1 random copolymer (melting point 148 as polypropylene resin
C., melting end temperature 161.degree. C., MI value 8 g / 10 min) except that resin particles and pre-expanded particles were obtained by the same method as in Comparative Example 1 and physical properties were measured. The results are shown in Table 8.

Comparative Example 7 Ethylene-propylene-butene-1 random copolymer as polypropylene resin (melting point 148 ° C., melting end temperature 161 ° C., MI value 8 g /
Resin particles and pre-expanded particles were obtained in the same manner as in Comparative Example 1 except that 10 minutes) were used, and the physical properties were measured. The results are shown in Table 8.

(Comparative Example 8) 2,6 having a molecular weight of 589 per unit triazine skeleton in place of isocyanuric acid
-Di-tert-4- (4,6-bis (octylthio)
-1,3,5-triazin-ylamino) phenol (trade name IRGANOX565 manufactured by Ciba Specialty Chemicals) was used, and resin particles and pre-expanded particles were obtained in the same manner as in Example 2 to measure physical properties. Was done. The results are shown in Table 8.

(Comparative Example 9) Instead of isocyanuric acid, the molecular weight per unit triazine skeleton was 784 1,
3,5-tris (3,5-di-tert-butyl-4-
Hydroxybenzyl) 1,3,5-triazine-2,
4,6 (1H, 3H, 5H) -trione (trade name IRG
Resin particles and pre-expanded particles were obtained in the same manner as in Example 2 except that ANOX3114 (manufactured by Ciba Specialty Chemicals) was used, and the physical properties were measured. The results are shown in Table 8.

The methods for evaluating the physical properties of the pre-expanded particles are shown below.

(Expansion Ratio) After measuring the weight of the pre-expanded particles,
The volume when immersed in ethanol in a 100 mL graduated cylinder was measured to obtain the true density, and the true density was calculated by dividing the density of the polypropylene-based resin composition resin particles by that value.

(Number of melting peaks of DSC curve in differential scanning calorimetry) From 1 to 10 mg of the pre-expanded particles were measured with a differential scanning calorimeter at a temperature rising rate of 10 ° C./min from 40 ° C. to 2 ° C.
The number of melting peaks in the DSC curve obtained when the temperature was raised to 20 ° C. was read.

(Open cell rate) The closed cell volume (V ₀ ) of the pre-expanded particles was determined using an air-comparison hydrometer (Beckman Model 930), and the ethanol immersion volume (V ₁ ) was separately set for the same sample. Then, the open cell rate (%) = ((V ₁ −V ₀ ) / V ₁ ) × 100 was calculated. As the open cell ratio increases, the moldability of the pre-expanded particles during in-mold foam molding deteriorates, and the mechanical strength such as the compressive strength of the in-mold foam molded article decreases. The open cell ratio is preferably 6% or less in order not to cause remarkable deterioration of moldability and reduction of mechanical strength.

(Average Cell Diameter) From the obtained preliminary particles, 30 pre-expanded particles were arbitrarily taken out, and JIS K6 was used.
The cell diameter was measured according to 402, and the average cell diameter (d) was calculated. The average cell diameter is 1 from the moldability when the pre-expanded particles are foam-molded in the mold, and the color when the foam-molded product in the mold is formed.
It is considered that about 100 to 500 μm is good. If the size is reduced to less than 50 μm, the moldability during in-mold foam molding tends to deteriorate.

(Cell diameter variation) The ratio (cell diameter variation U) of the average cell diameter (d) and the standard deviation (σ) representing the variation of the cell diameter is calculated by U (%) = (σ / d) × 100. did. The smaller U indicates that the cells are more uniform. The value of U was classified and evaluated according to the following criteria. ⊚: U value is less than 10% ◯: U value is 10% or more and less than 20% Δ: U value is 20% or more and less than 35% ×: U value is 35% or more (foaming ratio variation) Pre-expanded particles 0.3 to 1
L to JIS Z8801 standard sieve (3.5, 4, 5, 6,
Weight fraction W _i of pre-expanded particles remaining on each sieve when sieving with 7, 8, 9, 10 mesh) and expansion ratio K
_{From i} , the weighted average magnification K _av and the standard deviation σ _m are calculated by K _av = Σ (K _i × W _i ) σ _m = √ [Σ {W _i × (K _av −K _i ) ² }] Using the value of
_Was calculated by V (%) = (σ _m / K _av ) × 100. The smaller V indicates the smaller variation in the expansion ratio. The value of V is classified according to the following criteria,
evaluated. ⊚: V value is less than 7.5% ○: V value is 7.5% or more and less than 10% Δ: V value is 10% or more and less than 12.5% ×: V value is 12.5% or more Less than 15% XX: V value is 15% or more, as shown in Examples 1 to 7, 14 to 29, and 32 to 34,
(A) 100 parts by weight of ethylene-propylene random copolymer as polypropylene resin, and (B) ethylene- (meth) acrylic acid copolymer as hydrophilic polymer ion-crosslinked ethylene ionomer resin 0.01 to 20
As a compound having a triazine skeleton (C) and a molecular weight per unit triazine skeleton of 300 or less, isocyanuric acid, melamine or isocyanuric acid / melamine condensate 0.05 to 10 parts by weight, (D) an inorganic filler In the case of pre-expanded particles made of a polypropylene-based resin composition containing 0 to 10 parts by weight of talc, pre-expanded particles having a desired expansion ratio can be obtained, and variations in cell diameter and expansion ratio are small.

Further, as shown in Examples 1 to 7, 14 to 29 and 32, (C) isocyanuric acid, melamine or isocyanuric acid / melamine condensation is used as a compound having a triazine skeleton and a molecular weight per unit triazine skeleton of 300 or less. By adjusting the amount of the product added to 0.05 to 5 parts by weight, it is possible not only to reduce the variations in cell diameter and expansion ratio of the pre-expanded particles to be obtained, but also to reduce the open cell rate.

Further, as shown in Examples 8 to 13, even when mica, kaolin, bentonite, laponite, silica, or calcium carbonate is used as the inorganic filler, pre-expanded particles having small variations in cell diameter and expansion ratio can be obtained. . As shown in Examples 30 and 31, when a propylene-butene-1 random copolymer or an ethylene-propylene-butene-1 random copolymer was used as the polypropylene resin, the cell diameter variation and the foaming ratio variation were similar. Small pre-expanded particles are obtained.

On the other hand, as shown in Comparative Examples 1 to 7, it has a triazine skeleton and the molecular weight per unit triazine skeleton is 3
In the case where the compound of 00 or less was not added, the variation in cell diameter and the variation in expansion ratio of the pre-expanded particles obtained was found in Example 1.
It can be seen that it is larger than ~ 34.

Further, as shown in Comparative Examples 8 and 9, when a compound having a triazine skeleton but having a molecular weight per unit triazine skeleton of more than 300 was added, the cell diameter variation of the pre-expanded particles obtained, It can be seen that the variation in the foaming ratio is larger than in Examples 1 to 34.

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[Table 1]

[0084]

[Table 2]

[0085]

[Table 3]

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[Table 4]

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[Table 5]

[0088]

[Table 6]

[0089]

[Table 7]

[0090]

[Table 8]

[0091]

EFFECT OF THE INVENTION A foamable polypropylene resin composition comprising (A) a polypropylene resin, (B) a hydrophilic polymer, (C) a compound having a triazine skeleton and having a molecular weight per unit triazine skeleton of 300 or less. By using the resin particles, it is possible to obtain pre-expanded particles having less variation in expansion ratio and less variation in cell diameter. As a result, the variation in weight and the color unevenness in the case of the in-mold foam molded article are reduced.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C08L 101/04 C08L 101/04 F term (reference) 4F074 AA24 AA24A AA31 AA97 AA98 AD19 AG01 AG20 BA33 BC12 CA39 CC10X DA02 DA03 DA13 DA32 DA33 DA35 4J002 BB082 BB092 BB111 BB121 BB141 BB151 BB232 CF102 CL012 CL032 DE107 DE137 DE237 DJ037 DJ047 DJ057 EU186 FD017 FD206

Claims (10)

[Claims] 1. A foamable polypropylene comprising (A) a polypropylene resin, (B) a hydrophilic polymer, and (C) a triazine skeleton, and a compound having a molecular weight of 300 or less per unit triazine skeleton. -Based resin composition. 2. The hydrophilic polymer (B) is added in an amount of 0.01 to 20.
The expandable polypropylene-based resin composition according to claim 1, wherein the expandable polypropylene-based resin composition comprises a weight part. 3. A compound having a triazine skeleton (C) and having a molecular weight per unit triazine skeleton of 300 or less is 0.
05 to 5 parts by weight is included, The claim 1 or 2 characterized by the above-mentioned.
The expandable polypropylene-based resin composition described. 4. The expandable polypropylene resin composition according to any one of claims 1 to 3, further comprising (D) an inorganic filler. 5. The expandable polypropylene resin composition according to claim 4, wherein the inorganic filler (D) is contained in an amount of 0.005 to 10 parts by weight. 6. The polypropylene resin is one or a mixture selected from the group consisting of an ethylene-propylene random copolymer, a propylene-butene-1 random copolymer and an ethylene-propylene-butene-1 random copolymer. Item 6. The expandable polypropylene-based resin composition according to any one of items 1 to 5. 7. The expandable polypropylene according to claim 1, wherein the hydrophilic polymer is an ethylene-based ionomer resin obtained by crosslinking an ethylene- (meth) acrylic acid copolymer with an alkali metal ion. -Based resin composition. 8. A compound having a triazine skeleton and having a molecular weight per unit triazine skeleton of 300 or less is melamine,
The expandable polypropylene resin composition according to any one of claims 1 to 7, which is one or a mixture selected from the group of isocyanuric acid and a melamine-isocyanuric acid condensate. 9. A polypropylene resin pre-expanded particle comprising the polypropylene resin composition according to claim 1 as a base resin. 10. D obtained by differential scanning calorimetry
The polypropylene resin pre-expanded particles according to claim 9, which have two melting peaks in the SC curve.