JPH0873642A - Heat-resistant foamed product - Google Patents

Abstract

PURPOSE: To provide a heat-resistant foam which can be suitably used as a variety of heat insulating materials, cushioning materials and sealants because of its high heat resistance, insulation and flexibility. CONSTITUTION: This foam comprises a gel-free propylene resin having the relation represented by the formula, ηB/ηA=3.0-1,000 in B/A=10 (A, B are elongation strains on measurement of the sample and their strains are in 0.1-10) on its maximum value of the ratio of uniaxial melt elongation viscosity ηB/ηA in the elongation strains A and B at arbitrary two points where the tensile stress rate is measurable in the range of 0.01-1.0s-<1> where the expansion ratio of the foamed products is 5-200 and the closed cells occupy 5-70%.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a heat insulating material for piping, a heat insulating material for building materials, a cushioning material for packaging, a cushioning material for sports / leisure,
The present invention relates to a foam excellent in heat resistance, flexibility and heat insulation, which is suitable for use as a sealing material and the like.

[0002]

2. Description of the Related Art As a method for producing a polyethylene foam by extrusion foaming, JP-A-60-19520 discloses a method of extruding polyethylene grafted with alkoxysilane into a low pressure region from an extruder to obtain a foam. ing.

JP-A-60-31538 discloses a propylene polymer or a propylene-ethylene block copolymer having an ethylene content of 1 to 20% by weight and propylene-.
Disclosed is a method for producing a foam in which an inorganic gas is pressed into a mixture with an α-olefin copolymer to extrude and foam.

[0004]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
According to the method described in Japanese Patent Publication No. 0, since the cross-linking proceeds all at once immediately after the foaming by extrusion, a cross-linked foam having a high magnification can be obtained in a short period of time. Since it is crosslinked, it has higher heat resistance than uncrosslinked polyethylene, but it does not have the high heat resistance of polypropylene.

Further, the foam obtained by the method described in JP-A-60-31538 has a fine surface, and heat resistance is obtained, but a foam with a high magnification cannot be obtained. Insufficient heat insulation. Further, since the expansion ratio is low, it lacks flexibility and is not suitable for heat insulation of a bent portion of a pipe, for example.

The present invention solves the above conventional problems and provides a heat resistant foam which is excellent in heat resistance, heat insulation and flexibility and can be suitably used as various heat insulating materials, cushioning materials, sealing materials and the like. With the goal.

[0007]

The heat resistant foam of the present invention comprises:
Stretch strain rate is 0.01-1.0s^-1Can be measured within the range
A uniaxial axis at two arbitrary stretch strains A and B
Melt elongation viscosity η_A, Η _BThe maximum value of the ratio of
From a propylene-based resin that has a relationship and does not contain a gel component
Which has a foaming ratio of 5 to 200.
Also, the closed cell ratio is 5 to 70%.
Of. Η at B / A = 10_B/ Η_A= 3.0 to 1000 (A and B indicate the tensile strain amount of the sample at the time of measurement,
The amount of extension strain is in the range of 0.1 to 1.0. )

The propylene resin used in the present invention may be either a propylene homopolymer, a propylene-based copolymer, or a mixture thereof. An example of a copolymer containing propylene as a main component is propylene-
Examples include α-olefin copolymers. Examples of the α-olefin include ethylene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-butene, 1-pentene, and the like, and those containing 85% by weight or more of a propylene component are preferable. If the propylene component is less than 85% by weight, the heat resistance decreases, which is not preferable.

The propylene homopolymer and the copolymer containing propylene as a main component preferably have a melt index defined by JIS K7210 of 0.05 to 20, more preferably 0.1 to 15. is there. By having a melt index in this range, a foam having a high expansion ratio can be obtained by exhibiting appropriate fluidity in a molten state. However, if the melt index is less than 0.05, the melt viscosity is too high and foaming with a high expansion ratio is performed. It is difficult to obtain a body, and if it exceeds 20, the melt viscosity is too low and the elongation of the resin during foaming is poor,
It is easy to break the bubbles and a high-magnification foam cannot be obtained. The molecular weight of the propylene polymer and the copolymer containing propylene as a main component is preferably 50,000 to 500,000.

When the maximum value of η _B / η _A is less than 3.0,
There is no sudden viscosity increase in the molten resin during foaming and it easily flows, so only the thin film part of the bubble expands locally, and the expansion of the thick film part is delayed, so the bubble does not grow and the bubble breaks. As a result, a high-magnification foam cannot be obtained. The maximum value is 100
When it exceeds 0, the viscosity of the molten resin at the time of foaming increases rapidly, which hinders foaming and a foam with high magnification cannot be obtained. Therefore, the maximum value of η _B / η _A is 3.0 to
By setting to 1000, it is possible to obtain a high-magnification foam, and it is possible to further adjust the closed cell ratio to 5 to 70%. Melt index is 0.05 to 20
If the propylene-based resin is used, it is more effective in adjusting the closed cell ratio. _A more preferable range of the maximum value of η _B / η _A is 10 to 900.

If necessary, a bubble nucleating agent, an antioxidant, a pigment, an anti-shrink agent, a flame retardant, etc. may be added to the propylene resin.

The cell nucleating agent has an average particle diameter of 0.1 μm or more and 500 μm or less, and particularly 1 μm or more.
It is preferably 00 μm or less. If it exceeds 500 μm, the bubble diameter of the obtained foam becomes coarse and the surface smoothness is
It is not preferable because the heat insulating property is deteriorated. On the other hand, 0.1μ
If it is less than m, it becomes difficult to uniformly disperse the cell nucleating agent in the olefin resin, and a foam having uniform fine cells cannot be obtained, which is not preferable. Examples of the cell nucleating agent include calcium carbonate, talc, clay, magnesium oxide, zinc oxide, carbon black, silicon dioxide, titanium oxide, citric acid, sodium bicarbonate, orthoboric acid and talc, and alkaline earth metal salts of fatty acids. .

The antioxidant is not particularly limited as long as it is generally used, and examples thereof include tetrakis [methylene (3,5-di-t-butyl-4-hydroxyhydrocinnamate)] methane and thiodipropionic acid. Dilauryl, 1,1,3-tris (2-methyl-4-hydroxy-5-t-butylphenyl) butane and the like can be mentioned.

The shrinkage inhibitor is not particularly limited as long as it is commonly used, and for example, aliphatic hydrocarbon having a polar functional group is typical, and specifically, stearic acid monoglyceride, stearic acid amide and the like. is there.

Examples of the flame retardant include bromine flame retardants such as hexabromobiphenyl ether and decabromodiphenyl ether, phosphoric acid flame retardants such as ammonium polyphosphate, trimethyl phosphate and triethyl phosphate, melamine derivatives and inorganic flame retardants. Examples include one kind or a mixture of two or more kinds.

In order to produce the heat-resistant foam of the present invention, the propylene-based resin is brought into a molten state and a gaseous or liquid foaming agent is dissolved under high pressure, or the propylene-based resin is not added. In the molten state, a gaseous or liquid foaming agent is mixed and melted while maintaining a high pressure state, and the pressure is released to foam.

The blowing agent used is an aliphatic hydrocarbon such as butane, pentane, hexane, an aromatic hydrocarbon such as benzene, toluene, xylene, a ketone hydrocarbon such as acetone or methyl ethyl ketone, an alcohol such as methanol, ethanol or propanol. Halogenated carbonization of hydrocarbons, 1,1-dichloro-fluoroethane, 2,2-dichloro-1,1,1-trifluoroethane, 1,1,1,2-tetrafluoroethane, monochlorodifluoroethane, monochlorodifluoromethane, etc. Examples thereof include one kind or a mixture of two or more kinds selected from hydrogen, carbon dioxide gas, nitrogen gas, air, oxygen, inorganic gases such as neon and argon.
Among these, an inorganic gas that is highly safe and has no danger of depleting the ozone layer is particularly preferable, and among the inorganic gases, carbon dioxide having a high solubility in propylene-based resin, or a mixed gas of carbon dioxide and another gas is particularly preferable. .

The amount of the foaming agent dissolved is 1 g of propylene resin.
On the other hand, it is preferably 5 to 200 cc at room temperature and atmospheric pressure. If it is less than 5 cc, a high-magnification foam cannot be obtained, and the heat insulating property of the foam deteriorates. If it exceeds 200 cc, further heat insulating properties are not improved and it is wasteful.

The resin temperature T when the pressure is released by the above manufacturing method is preferably the melting point (Tm) of the resin + (+ 5 to 50 ° C.). When T <Tm + 5 ° C., the closed cell rate becomes high, and the flexibility may be impaired. In such a case, a foam having a high closed cell ratio is produced within the range of Tm-10 ° C <T <Tm + 5 ° C, and a large number of perforations are provided in the foam to make the closed cell ratio 5 to 70%. You may adjust. T
When> Tm + 50 ° C., the melt viscosity of the resin is low, so that the foaming is severe at the time of foaming, and a high-magnification foam cannot be obtained.

An extrusion foaming device or a pressure resistant container is used as a means for producing the foam. In the method using an extrusion foaming device, a propylene-based resin is charged into a hopper of an extruder, and a foaming agent is pressed into a gas injection hole provided in a portion where the resin is in a molten state. When carbon dioxide is used as the foaming agent, the pressure of the press-fitting hole attached to the extruder is 15 to 6
When injected at a rate of 00 kg / cm ² , a dissolved amount within the above range can be obtained.

As the injection method, there are a method of directly injecting a gas adjusted to a predetermined pressure, a method of injecting a liquid foaming agent at a predetermined pressure using a plunger pump or the like.
Alternatively, the resin may be impregnated with a foaming agent under high pressure in advance, and the resin may be charged from the hopper of the extruder. In this case, it is preferable to use a pressure hopper because gas is released before it becomes a molten state in the extruder and may escape from the hopper, and a foaming agent that is insufficient to obtain the target expansion ratio is extruded. Press in from the middle of the machine.

Then, the resin in which the foaming agent is dissolved is introduced into a mold maintained at the temperature T and extruded from a die having a desired shape into the atmospheric pressure to foam due to a pressure difference to obtain a desired foam. To be The shape of the die at this time may be a shape that is sequentially expanded into a shape according to the desired foam,
It may also be lubricated with lubricating oil. Further, in order to maintain the shape of the foam, it may be brought into contact with a refrigerant such as water or cold air having a temperature lower than the softening point of the resin at the moment of extrusion from the die.

As a method of manufacturing using a pressure resistant container,
A resin and a foaming agent are kneaded and melted with a roll or an extruder to form a desired shape, and the mixture is put into a pressure resistant container. Then, the resin is heated to a temperature suitable for foaming, and a foaming agent is press-fitted and dissolved in the resin. The foaming agent may be pressed and dissolved before heating. When carbon dioxide gas is used as the foaming agent, the pressure of the foaming agent is preferably 15 to 600 kg / cm ^2, and the dissolution amount is suitable in this pressure range.

The foaming agent may be injected by directly injecting a gas adjusted to a predetermined pressure, by injecting a liquid foaming agent with a plunger pump, or by injecting it in a solid state. After the inorganic gas is sufficiently dissolved in the resin, the target foam can be obtained by opening the pressure valve of the pressure vessel.

The heat-resistant foam of the present invention has an expansion ratio of 5 to 20.
It is 0 times. A more preferable range is 10 to 150 times. If the expansion ratio is less than 5 times, the heat insulation is poor and
Even if it exceeds twice, not only the heat insulating property is not further improved but also the strength is reduced.

The closed cell ratio of the heat resistant foam of the present invention is 5
~ 70%. A more preferred range is 10 to 65%. If the closed cell ratio is less than 5%, the number of open cells becomes large, the water absorption is large, and the heat insulating property is deteriorated, which is not preferable. If it exceeds 70%, the flexibility of the foam will be insufficient, and if it is bent, it will be easily broken.

In the present invention, the use of a propylene-based resin containing no gel component makes it possible to obtain a high-magnification foam, and appropriate foam breakage occurs during foaming, so that the closed cell ratio can be easily adjusted. This is because the foam can be collected and reused. When the resin contains a gel component, that is, when it is crosslinked, the foamed bubbles do not grow greatly, and it is difficult to form a foam with a high magnification, and it is difficult for bubble breakage to occur and most of the cells become closed cells. It is difficult to adjust the bubble rate to 5 to 70%. In addition, the crosslinking makes it difficult to reuse.

[0028]

The heat-resistant foam of the present invention is excellent in heat resistance because it is made of a propylene resin. Propylene resin to be used, elongation strain rate each melt extensional viscosity eta _A at any two points can be measured within the 0.01～1.0S ^-1, the ratio η _B / η _A of eta _B Maximum value is 3.0 to 1000
Within this range, the resin will have an appropriate increase in viscosity during foaming, the resin will have good elongation, and a high-magnification foam can be obtained. Since the propylene-based resin used does not contain a gel component, it can be made to have a high expansion ratio of 5 to 200 times and a closed cell ratio of 5 to 70%, and can be easily reused.

[0029]

EXAMPLES Examples of the heat resistant foam of the present invention will be described below. The following was used as the propylene-based resin. (1) Polypropylene (manufactured by Himont, trade name "P
F814 ”, MI = 4, melting point 165 ° C., gel component 0) The elongation strain amount A measured at an elongation strain rate of 0.4 s ⁻¹ is 0.86.
Uniaxial melt extensional viscosity η _A = 21544 Pa · s,
Uniaxial melt extensional viscosity η _B = 8 when the extensional strain amount B is 8.6
It was 43190 Pa · s and η _B / η _A = 39.1. (2) Random copolymer of propylene and ethylene (manufactured by Chisso Petrochemical Co., Ltd., trade name "XF1800", MI =
2, melting point 146 ° C.) The tensile strain amount A measured at a tensile strain rate of 0.4 s ⁻¹ is 0.19.
Uniaxial melt extensional viscosity η _A = 234462 Pa · 4
s, uniaxial melt extensional viscosity η at elongation strain B of 1.94
_B = 48438 Pa · s, η _B / η _A = 1.85
Met.

Example 1 Polypropylene (PF81
4) 100 parts by weight and 0.8 as a bubble-forming nucleating agent (manufactured by Nippon Talc Co., Ltd., trade name “MS”, average particle size 9 μm) 0.8
Part by weight and charged into the hopper of a vent type extruder (caliber 65 mm, L / D = 35) set to 210 ° C.,
Carbon dioxide gas was press-fitted at a pressure of 50 kg / cm ² from the vent part, and 12 kg from a cap with a diameter of 2 mm set at 171 ° C.
It was extruded into a rod shape at a discharge amount of / h and foamed.

(Example 2) Extrusion foaming was carried out in the same manner as in Example 1 except that talc was not used, the pressure of carbon dioxide gas injected from the vent was 100 kg / cm ² , and the temperature of the die of the extruder was 190 ° C. did.

(Example 3) Extrusion and foaming were carried out in the same manner as in Example 1 except that talc was not used and the pressure of carbon dioxide gas injected from the vent was 100 kg / cm ² .

Example 4 Monochlorodifluoroethane (Freon) was used instead of carbon dioxide gas without using talc, the pressure of the vent portion was 100 kg / cm ² , and the temperature of the die of the extruder was 172 ° C. Except for this, extrusion was performed and foaming was performed in the same manner as in Example 1.

(Example 5) Example 4 except that the press-fitting pressure of monochlorodifluoroethane was set to 120 kg / cm ^2.
It was extruded and foamed in the same manner as in.

Example 6 100 parts by weight of the same polypropylene as used in Example 1 and 0.8 parts by weight of talc were kneaded with a roll set at 200 ° C.
The sheet was pressed at 00 ° C. and a pressure of 150 kg / cm ² for 5 minutes to obtain a sheet having a thickness of 2 mm. The sheet was put into an autoclave set at 169 ° C., and carbon dioxide gas pressure was 500 kg.
/ Cm ^{2 and} after heating for 2 hours, the pressure reducing valve was opened to foam and obtain a foam. The obtained foam was put into an autoclave set at 100 ° C., and the nitrogen gas pressure was 8 k.
It was cured for 8 hours at g / cm ² . The obtained foam had an expansion ratio of 150 cc / g and a closed cell rate of 82%. A hole was made in this foam with a needle to adjust the closed cell ratio to 61%.

(Comparative Example 1) Extrusion and foaming were carried out in the same manner as in Example 1 except that the pressure of the carbon dioxide gas injected from the vent was 10 kg / cm ² .

(Comparative Example 2) Extrusion and foaming were carried out in the same manner as in Example 2 except that talc was not used and the temperature of the die of the extruder was 165 ° C.

Comparative Example 3 The foam obtained in Comparative Example 2 has a large number of holes formed by needles.

(Comparative Example 4) Extrusion and foaming were carried out in the same manner as in Comparative Example 2 except that the temperature of the die of the extruder was changed to 157 ° C using a copolymer of propylene and ethylene (XF1800). Table 1 shows the production conditions for the foams of Examples 1 to 6 and Comparative Examples 1 to 4.

[0040]

[Table 1]

The performance evaluation results of the foams of Examples 1 to 6 and Comparative Examples 1 to 4 are shown in Table 2. The evaluation method is as follows. Adiabatic property; thermal conductivity measured at 0 ° C. Flexibility; judged by whether or not it is bent at 90 degrees. Heat resistance; after 22 hours at 120 ° C, 20 ° C, humidity 65
The dimensional change rate after 1 hour in%. Water absorption rate: Measured according to JIS K6767.

[0042]

[Table 2]

As is apparent from Table 2, in Examples 1 to 6, the expansion ratio is in the range of 5 to 200 times, and
It can be seen that since the closed cell ratio is in the range of 5 to 70%, the water absorption rate is low and the heat insulating property is good while having flexibility. On the other hand, Comparative Example 1 has a low expansion ratio of 3 times, and Comparative Example 2 has a closed cell ratio of more than 70%, so that it has almost no flexibility even if the water absorption rate is low. Further, in Comparative Example 3, the closed cell ratio is 0%, that is, all of them are open cells, so that even if they have flexibility, they have a high water absorption rate and cannot obtain heat insulation. Since the foaming ratio of Comparative Example 4 is as low as 4 times, there is no flexibility,
Since most of the few bubbles are open cells, the amount of water absorption is large and the heat insulation is extremely low.

[0044]

The heat-resistant foam of the present invention is excellent in heat resistance since it is made of a propylene resin. Further, it is a high-magnification foam and is highly flexible, while it has a low water absorption rate, so it has excellent heat insulating properties, and is extremely practical as a heat insulating material, cushioning material, or sealing material in various applications.

Claims (1)

[Claims] 1. _A ratio of uniaxial melt extensional viscosities η _A and η _B at arbitrary two points of extensional strain A and B which can be measured within an extensional strain rate of 0.01 to 1.0 s ^−1. Has a relationship represented by the following formula, and is a foam made of a propylene-based resin containing no gel component, the foaming ratio of the foam is 5 to 200 times, and the closed cell ratio is 5 to 70%. A heat-resistant foam characterized by the following. Η _B / η _{A at} B / A = 10 = 3.0 to 1000 (A and B indicate the tensile strain amount of the sample at the time of measurement, and the tensile strain amount of A is within the range of 0.1 to 1.0. is there.)