JPS5829809B2 - Ethylene cage - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to ethylene resin particles that can be foamed and molded by heating. The present invention relates to expandable ethylene resin particles that can shorten the time required for in-mold molding when performing foam molding, and can provide a high-quality foam molded product that is filled with homogeneous fine air to the core of the molded product.

Conventionally, there has been much research into foaming pre-foamed ethylene resin particles to obtain molded bodies.

For example, the methods disclosed in JP-A No. 47-34458 and JP-A No. 49-85158 fall under these methods, and both require the use of crosslinked ethylene resins.

In general, compared to polystyrene resin, ethylene resin is
Since it is impossible to obtain molded foams industrially because the viscoelastic flow properties of the resins are different and the permeability of gases such as blowing agent gases is fundamentally different, crosslinking is used to improve the basic properties. need to be done.

However, crosslinking ethylene resins, regardless of the method used, poses many technical and economical difficulties, and not only ultimately results in a loss of economic efficiency, but also the ability to crosslink properly. Even if the crosslinked ethylene resin particles are intended to be treated, it is impossible to make the properties close to those of polystyrene resin, so it is difficult to foam-mold the particles.

For example, Example 10 of JP-A-4'9-85158
The expandable crosslinked particles obtained in the above have an internal pressure of 166 atm, and even if the expandable particles are left in the atmosphere for 40 minutes or 80 minutes,
It is stated that the internal pressures of these are 1.25 and 1.18 atm, respectively, and that when these are molded, a molded product with an excellent fusion index can be obtained, but according to additional tests by the present inventors,
Not only did the measured internal pressure values not match, but even foam molding was not possible, let alone fusion between particles.

Furthermore, it was difficult to mold particles even at an internal pressure of 14 atmospheres.

Therefore, it is reasonable to assume that the technology for forming beads using ethylene fat particles has not been completed industrially to date.

The present invention has been made in view of the above-mentioned current situation, and has finally been achieved by organically combining the requirements of using an ethylene resin with a special component and determining the internal pressure of the air bubbles within the particles when they are made into pre-expanded particles. The purpose of this product is to provide expandable ethylene resin particles that can be foam-molded to the same degree as bead molding of polystyrene resin, even with substantially non-crosslinked ethylene resin particles, thereby making it economical. Specifically, the objective is to perfect the manufacturing technology of better quality ethylene resin foam molded products.

That is, the present invention provides ethylene containing 0.1 to 10% by weight of a partial ester of a fatty acid having 12 to 18 carbon atoms and a polyol having 3 to 6 hydroxyl groups, and 2 to 50% by weight of an ionic copolymer. Pre-expanded particles of a resin based resin,
Moreover, non-crosslinked expandable ethylene resin particles are provided in which the air bubbles of the particles are filled with gas at 1.2 to 4 atm.

One of the important requirements of the present invention is the use of a specific amount of an ionic copolymer and a specific amount of a specified ester mixed with the ethylene resin.

The combined use of this ionic copolymer and a specific ester has the revolutionary advantage of making it possible to perform bead foam molding using ethylene resin particles in a non-crosslinked state, which was previously considered impossible. It also has the advantage of being more stable under molding conditions than conventionally known foamable crosslinked ethylene resins.

The relationship between this advantage and the composition is such that, for example, if both the ionic polymer and the specific ester are missing in the ethylene resin particles, the advantage cannot be obtained if either one is missing, and if the amount of the ionic polymer is When the weight percentage is less than 2% and more than 50%, the benefits tend to decrease.

Therefore, the most desirable range is considered to be 5 to 45%.

On the other hand, the amount of the specific ester is less than 0.1 in weight proportion,
The advantage also tends to decrease when the amount exceeds 10%, and the most desirable range is 0.5 to 10%.
%it is conceivable that.

In addition, in the present invention, it is necessary to use a partial ester with a fatty acid having 12 to 18 carbon atoms and a polyol having 3 to 6 hydroxyl groups; other partial esters are , the expected benefits of the present invention are reduced or not obtained.

Next, the second important requirement of the present invention is that even if the pre-expanded particles are made by pre-foaming the ethylene resin composition having the above-mentioned composition, the air bubbles of the expanded particles must have a pressure of 1.2 to 4 atm. (absolute pressure), most preferably 1.3 to 3.7 atmospheres.

When molding on an industrial production basis using the particles of the present invention,
When the internal pressure of the expandable particles is within the range of 1.2 to 4 atmospheres, molding can be performed at low temperatures and in a short time, leading to improved molding ability and simplification of the molding process. The effect is that excellent molded bodies can be easily produced with little variation.

Although the theoretical elucidation of these effects is not clear at present, it is believed that the gas barrier effect of the specific ester in the present invention and the selective gas barrier effect of the ionic copolymer are the same. It is thought that the heat resistance of the resin, the viscoelastic flow characteristics of the resin, etc. act synergistically in a well-balanced state, realizing a state suitable for bead foam molding of non-crosslinked ethylene resin particles.

The ethylene resin used as a raw material for the present invention is a general term for homopolymers, copolymers, and blend polymers containing 50% by weight or more of ethylene.

Specifically, for example, high-pressure polyethylene, ethylene-vinyl acetate copolymer, ethylene-methyl methacrylate copolymer, etc. are most preferred; Polymers can also be used, and mixtures of two or more of the above various polymers and mixtures with styrene polymers and various rubbers can also be used.

The ionic copolymer referred to in the present invention is one having an α-olefin content of 50 mol% or more and an α/β-ethylenically unsaturated mono- or dicarboxylic acid content of 0.2 to 25 mol%, and is based on ASTM - Is the melting index measured by the method described in D-123857T 01-100L? /10 min.
The valence of the metal ion is 1 to 3 when the acid monomer component is a monocarboxylic acid, and 1 when it is a dicarboxylic acid.

) to neutralize the carboxylic acid groups of the above copolymer, and the degree of neutralization calculated from the absorption degree of the absorption band by infrared spectroscopy is 10 to 40%. If a substance has cross-bonds but melts, the cross-bonds disappear or decrease and it returns to the solid state again.
It refers to a copolymer in which the cross bonds are restored.

The α-olefin which is the main component of the above ionic copolymer is represented by the general formula RCH=CH2.

In this case, R is hydrogen or an alkyl group, and the alkyl group preferably has 1 to 8 carbon atoms.

Suitable olefins include ethylene, propylene, phthene-1, pentene-1, hexene-1,3-methylbutene-1,4-methylpentene-1, and the like.

Furthermore, polymers of olefins having a large number of carbon atoms can also be used.

The concentration of α-olefin in the copolymer is at least 50 mol% and preferably greater than 80 mol%.

The second component of the ionic copolymer is preferably an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms.

Examples of such monomers include methacrylic acid, itaconic acid, maleic acid, fumaric acid and monoesters of these dicarboxylic acids, such as methyl hydrogen maleate, methyl hydrogen fumarate, ethyl hydrogen fumarate and maleic anhydride. It is.

Although maleic anhydride is not a carboxylic acid, it has the same chemical reactivity as an acid and therefore can be considered an acid for the purposes of this invention and can be used similarly.

Similarly, other α/β-monoethylenically unsaturated carboxylic acid anhydrides can also be used.

As mentioned above, the concentration of the acidic copolymer component in the copolymer is 0.2 to 0.25 mol%, most preferably 1 to 0.25 mol%.
It is 10 mol%.

The metal ion component of the ionic copolymer is particularly a metal ion of groups 1, 2, 2, IV-a, and 2 with a periodicity of 1 to 1.
It has a valence of 3.

For example, monovalent metal ions include Na+, K-'I-
.

Li+, Ag+, Cu+ and divalent metal ions include B++, M8++, ca++, sr++, Ba++
, cu++, cd++ sn++, Pb++, Fe++
, Co++, Ni++, and Zn++, and trivalent metal ions include Sc+++, Fe+++, Yt+++, and the like.

In the present invention, an alkali metal is preferable.

The ionic copolymer has a melting index of 0.1 to 30 f710 min, preferably 0.5 to 209710 min, as measured by the method described in ASTM-D-1238-57T. belongs to.

The limits placed on the ionic copolymers mentioned above are 12 carbon atoms.
It is moderately compatible with a mixture of crystalline polyolefin and a partial ester of ~18 fatty acids and a polyol having 3 to 6 hydroxyl groups, has mechanical properties as a plastic, and has excellent properties during foam molding. This is a necessary condition to simultaneously improve extrusion processability and shrinkage prevention effect.

Typical partial esters of fatty acids having 12 to 18 carbon atoms and polyols having 3 to 6 hydroxyl groups used in the present invention include, for example, glyceryl monostearate, glyceryl distearate, mono- and Mention may be made of mixtures of di-glycerol esters, mono-, di- and tri-sorbitan oleate, mono- and di-glycerol esters of oleic acid, palmitic acid.

Additionally, mixtures of these substances are also useful.

The blowing agent used in the process of the present invention can be any hydrocarbon and halogenated hydrocarbon that boils below the melting point of the polyolefin.

Examples of desirable hydrocarbons include pentane, hexane,
Compounds such as heptane and octane may be mentioned.

Desirable halogenated hydrocarbons that satisfy the same restrictions regarding boiling point include, for example, methylene chloride, dichlorodifluoromethane (hereinafter abbreviated as F-12), trichlorofluoromethane (hereinafter abbreviated as F11), dichlorofluoromethane (hereinafter abbreviated as F-12), dichlorofluoromethane (hereinafter abbreviated as F11), -21), dichlorotetrafluoroethane (hereinafter abbreviated as F-114)
There is.

Also useful are mixtures of these materials. The expandable particles of the present invention are produced by mixing the ionic copolymer, the specific ester, and the ethylene resin in the form of pre-expanded particles.

As a method for producing pre-expanded particles, a wide variety of conventionally known methods can be applied.

For example, an ionic copolymer, a specific ester, and an ethylene resin are supplied to an extruder, melt-kneaded, mixed with a blowing agent, and extruded at a low temperature to obtain pre-expanded particles. a method of heating and foaming the polypropylene particles to obtain pre-expanded particles, and a method of directly obtaining pre-expanded particles by proceeding foaming simultaneously with the extrusion, or L is an ionic copolymer;
A specific ester or ethylene resin is mixed and kneaded in an extruder, mixer, roll mill, etc., cut and crushed to create mixed resin particles, and the mixed resin particles are brought into contact with and impregnated with a blowing agent. Methods such as heating and foaming to form pre-expanded particles can be used, but in the case of the present invention, mixed resin particles are created using an extruder or the like, and mixed with water-soluble polymeric substances such as polyvinyl alcohol, calcium phosphate, etc.
Contains substances selected from dispersants of poorly soluble inorganic substances such as magnesium carbonate, vermiculite powder, mica powder, and talc, and surfactants such as sodium dodecylbenzenesulfonate, polyethylene glycol, and polyoxyethylene octylphenyl ether. The most excellent method for producing pre-expandable particles is to suspend them in an aqueous solution, heat treat them, and then incorporate a blowing agent into the mixed resin particles.

Normally, it is desirable for the final expandable particles to be truly spherical in order to obtain a foamed molded product, but it is usually extremely difficult to obtain truly spherical expandable particles.

However, in implementing the present invention, the M and I of the ethylene resin as a raw material are set to 3 to 30 (more strictly, 5 to 23).
If pre-expanded particles are produced by using aqueous suspension method in combination with the above-mentioned aqueous suspension method, even if the shape of the mixed resin particles is extremely non-spherical, it is easy to make the particles into true spherical particles. This is advantageous because it has the ability to

In addition, the above mixed resin may contain 0.05 to 5% by weight if necessary.
In addition to mixing commonly used nucleating agents within the range of
Additives such as lubricants can also be mixed.

The blowing agents for the above-mentioned pre-foaming are generally chemical blowing agents represented by azodicarboxylic acid amide, dinitrosopentamethylenetetramine, etc., and hydrocarbons boiling below the melting point of the resin, halogenated hydrocarbons, etc. Physical blowing agents, inorganic gases represented by nitrogen, air, etc., and mixtures thereof can be used, but from the viewpoint of shrinkability, workability, and economic efficiency of pre-expanded particles, for example, pentane, hexane, heptane, octane, methyl Preference is given to using chloride, dichlorofluoromethane, dichlorofluoroethane and mixtures thereof.

The pre-foamed particles that have undergone pre-foaming are foamed to a foaming ratio of 15 to 35 times when expressed as the foaming ratio, which is the ratio of bulk removal 0 for a unit weight (ri) of foam, that is, cc/f, The particle size is about 2 to 15 mm.

The expandable particles as used in the present invention are obtained by making the pre-expanded particles contain a blowing agent gas again and adjusting the gas pressure within the bubbles of the particles.

As the blowing agent in this case, the above-mentioned physical blowing agent, inorganic gas, or a mixed gas thereof will be used, but in order to improve the sustainability of molding performance, it is advantageous to use an inorganic gas, especially nitrogen or air. Become.

This is thought to be due to the fact that the ionic copolymer contained in the pre-expanded particles selectively blocks gas.

In addition, in the present invention, sufficient molding and foaming can be carried out without crosslinking the ethylene resin, but this does not particularly preclude the use of crosslinking in combination with the present invention.

When it is desired to use crosslinking treatments in combination as necessary, the purpose can be easily achieved by adopting appropriate means for each crosslinking treatment at an appropriate point in the process from the raw resin to the foamed molded product.

In addition, the method of incorporating blowing agent gas into pre-expanded particles is as follows:
This is usually achieved by holding the pre-expanded particles in a blowing agent gas under high pressure.

In this case, the conditions are that the gas pressure of the blowing agent is 3 to 30
Appropriate conditions are selected for kg/aA (gauge pressure) and temperature from a range below the melting point of the resin.

In other words, the higher the gas pressure and the higher the temperature, the higher the gas permeation rate and the shorter the processing time, but in order to fully impregnate the core of the particles with gas, the gas pressure must be 8 to 8.
18 kg/crty (gauge pressure) temperature 40-60
℃ or so for a relatively long period of time, and particles treated under a high pressure of, for example, about 8 to 20 kg/ctA (gauge pressure) are treated at a low pressure of, for example, about 0.5 to 3 to 9/cr7t (gauge pressure). It is desirable to carry out a two-stage operation, such as aging under a second stage.

After the internal pressure has been adjusted, the expandable particles have an internal pressure of 1.2~
Fill the mold while the pressure is at 4.0 atm, about 80~15
By applying a temperature of 0°C, it foams and becomes a high-quality foam molded product that conforms to the inner shape of the mold.

As a heating method in this case, for example, known heating means such as steam, hot air, and high frequency heating can be used, but a closed mold having small holes is used as the mold, and steam heating and hot water heating are performed. This is also an excellent method in terms of thermal efficiency.

In the present invention, the internal pressure of the cells of the expandable particles is determined by measuring the expansion ratio α (CC/P) and the total weight (ri) of the expandable particles whose internal pressure is to be measured. The volume of gas released from the expanded particles was sealed in a container and left to stand for 24 hours, and the volume of gas released from the expanded particles was captured and measured under atmospheric pressure using a bilulet. Obtained by the formula.

However, dp is the density of the base resin.

Next, the present invention will be explained in more detail with reference to Examples.

Example 1 Low density polyethylene (density 0.921M, I, 11
), stearic acid monoglyceride [trade name Atomul 8]
0 (manufactured by Kao Soap Co., Ltd.)] and an ionic copolymer [trade name Surlyn A-1706 (manufactured by Mitsui Polychemical Co., Ltd.)] were blended in the proportions shown in the composition column of Table 1. Add 0.5 parts of zinc stearate and 05 parts of calcium silicate to each 100 parts (hereinafter referred to as parts by weight) of the resin,
Kneaded and extruded in an extruder with a diameter of 30 mm,
．． A beret with a length of 1 mm and a length of 1.5 mm was made.

100 parts of each of these pellets, 100 parts of water, and 15 parts of magnesium carbonate were placed in an autoclave and heated to 150°C for 1.
When the mixture was heated with stirring for 5 hours, cooled, washed, and taken out, straight spherical particles with a diameter of about 1.9 mm were obtained.

These particles were placed in a pressure-resistant container, liquid dichlorofluoromethane (hereinafter abbreviated as Freon-12) was introduced under pressure, and the temperature was increased to 60°C.
Stir Freon-12 and particles while directly contacting them at a temperature of , impregnate the particles with Freon-12, cool them, take them out, and heat them with steam at 100°C for 10 to 20 seconds to obtain a foaming ratio of 25 times (CC/?). Pre-expanded particles with a diameter of about 57n711 were made.

Next, each of these particles was placed in a pressure-resistant container, and treated under air pressure of 50' C10 kg/crij gauge pressure for 10 to 15 hours.
The temperature was lowered to ℃ and taken out.

The internal pressure of the obtained expandable particles was adjusted within the above treatment time range according to the difference in resin composition of the particles so that all the particles exhibited approximately 2 atmospheres.

Take out a portion of each of these expandable particles, leave it under atmospheric pressure, mold it at intervals of 5 minutes, and find out how long the expandable particles are left until sink marks appear on the molded product. was evaluated as the sustainability of molding ability, and this is listed in Table 1.

Furthermore, the suitability of the molding conditions was evaluated using particles whose internal pressure was maintained at 2 atm.

The evaluation conditions are as follows: Molding humidity is set at 5°C intervals between 85°C and 150°C, heating time is set between 10 seconds and 40 seconds at 5 second intervals for each temperature, and the quality of the molded product obtained is determined. The results were examined in detail and evaluated based on the wide range of conditions under which a commercially valuable molded product without any defects could be obtained, as well as the size of the variation in quality when repeated experiments were performed.

The molding machine used for the above molding was EC manufactured by Toyo Machinery & Metals.
The mold used in the HO-120 molding machine had a thickness of 30 mm,
The mold was of a closed type with length and width of 300 mm each, and had a large number of small holes in the wall of the mold.

Example 2 Low density polyethylene (density 0.921M, 1.5)
88% to 85%, 10% of the ionic copolymer [trade name Surlyn A to 1602 (manufactured by Mitsui Polychemical Co., Ltd.)] and the second
Mix 2 to 5% of the specific ester shown in the table so that the total is 100, and make 100 parts (by weight) of this mixture.
0.4 parts of zinc stearate, 0 parts of calcium silicate
．． Add 6 parts and knead in an extruder with a diameter of 30 mm,
Next, about 21 parts of dichlorotetrafluoromethane (hereinafter abbreviated as Freon 114) was injected into the extruder, dispersed in the resin, extruded under atmospheric pressure at a resin temperature of about 100°C, and cut to give an expansion ratio of 23 times. , - Foamed particles in the shape of a vertical cube with sides of about 6 mm were created.

This was maintained at 60°C in an air atmosphere of 15 to 9/cr7r gauge pressure for 7 hours, and then heated to 25°C while maintaining the pressurized state.
The temperature was lowered to 100% and the foamed particles were taken out.

The internal pressure of the expandable particles obtained was approximately 2.5 atm.

These expandable particles were left under atmospheric pressure, and the bottom was shaped at intervals of 5 minutes, and the duration of the expandable particles until sink marks appeared on the molded product was determined as the sustainability of the molding ability. The results are listed in Table 2.

The molding machine used in this case was the same as in Example 1.

Example 3 High density polyethylene (density 0.945M, I, 18
) 93%, stearic acid monoglyceride [trade name Atomul T-95 (manufactured by Kao Soap Co., Ltd.)] 11% ionic copolymer [trade name Surlyn A-1650 (manufactured by Mitsui Polychemical Co., Ltd.)] 6%, zinc stearate 0. 4% of calcium silicate and 0.5% of calcium silicate were premixed, and the mixture was kneaded and extruded in an extruder having a diameter of 3.0 mm to produce pellets with a diameter of 2 mm and a length of 1.5 mm.

100 parts of these pellets, 100 parts of water, and 1.5 parts of magnesium carbonate were placed in an autoclave and heated to 1.50°C for 1.
When the mixture was heated with stirring for 5 hours, cooled, washed, and taken out, true spherical particles of 2.6 mm were obtained.

These particles are placed in a pressure-resistant container, propane is pressurized, the particles are impregnated with propane, and heated with steam at 110°C for 15 seconds to achieve a diameter of approximately 77 rtrr with an expansion ratio of 25 times (CC/?).
L pre-expanded particles were made.

Next, these particles were placed in three pressure-resistant containers, each filled with nitrogen, air, and Freon 114, and the pressure, temperature, and treatment time were adjusted in the same manner as in Example 1, so that the internal pressure inside the foamed particle bubbles was adjusted to the same level as in Example 1. Regarding gas, ], 1, 1.2.2
．． Expandable particles exhibiting pressures of 1, 2, 8, 3, 7, 40, and 4.5 atmospheres were prepared.

These expandable particles were molded using the same mold and molding machine as in Example 1.
Under a heating temperature of 00'C, 5 seconds to 40 seconds were incremented at 5 second intervals, which was used as the heating time, and the quality of the molded product obtained under the conditions for foam molding was evaluated. As shown in the figure.

According to this, it can be seen that the internal pressure of 1.5 to 40 atm has a wide suitable range of conditions on the low pressure side, although the range varies somewhat depending on the added gas.

A, B, C, and D in this figure are reference drawings A and B, respectively.

The foaming states are shown in C and D, where A indicates good foaming, B indicates insufficient foaming, C indicates insufficient foaming only in the core, and D indicates sinking.

[Brief explanation of the drawing]

FIG. 1 is a state diagram showing the relationship between molding conditions and foaming state in Examples and Comparative Examples of the present invention.

Claims (1)

[Claims] 1 Partial ester of fatty acid having 12 to 18 carbon atoms and polyol having 3 to 6 hydroxyl groups 0.1 to 10
Non-crosslinked pre-expanded particles of ethylene-based resin containing 1% by weight and 2 to 50% by weight of an ionic copolymer, and in which the air bubbles of the particles are filled with gas at 1.2 to 4 atm. expandable ethylene resin particles.