JP2527925C - - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to an improved method of forming a thermoplastic foam from an alkenyl aromatic polymer material. In particular, it is a method for producing a styrene polymer foam by an extrusion method widely used in the field of heat insulating materials. Thermoplastic foams are widely used in the field of thermal insulation. Of particular interest in this field are styrene polymer foams. Thermoplastic foam materials suitable for use in the field of insulation are desirably extruded foams having a generally uniform cell size. [0002] In the prior art, methods for producing extruded thermoplastic foam materials are well known. Typically, the steps of such a manufacturing method include: (1) thermoplasticizing the alkenyl aromatic polymer material to be foamed; and (2) applying a pressure sufficient to inhibit foaming of the thermoplasticized polymer material. Adding a volatile fluid blowing agent to the polymeric material while intact; and (3) forming a foam by volatilizing the blowing agent by extruding the blowing agent / polymer material mixture into a region of low pressure. Inducing. [0003] Such methods are disclosed in US Patent Nos. 2,409,910, 2,525,250,
Nos. 2,699,751, 2,848,428, 2,928,130,
No. 3,121,130, No. 3,121,911, No. 3,770,688,
Nos. 3,815,674, 3,960,792, 3,966,381,
Nos. 4,085,073 and 4,146,563. One particularly desirable method for producing stable styrenic polymer foams is US Pat. No. 3,960,792 [M. Nakamura (M. Nakamura)]. This patent describes a method for making a styrenic polymer foam using a blowing agent mixture of methyl chloride and chlorofluorocarbon. While the use of methyl chloride as a blowing agent produces foams with very desirable physical properties as thermal insulation, the use of methyl chloride is undesirable in some respects. Due to the stringent industrial hygiene requirements associated with methyl chloride, foams using methyl chloride as blowing agent allow methyl chloride to escape from the bubbles and allow air to enter through the cell walls (membrane) by suitable diffusion methods Must be aged for a sufficient period of time. Obviously, the length of time that the foam material must be aged depends on the thickness of the foam material. When manufacturing relatively thick sheets of foam material, the need for a relatively long aging period can present disadvantageous warehouse housing problems. [0005] Due to the aforementioned disadvantages inherent in the use of methyl chloride as a blowing agent, one or more blowing agents for producing foams that have desirable physical properties but do not have the aforementioned problems will be found. A lot of work has been done with effort. In U.S. Pat. No. 2,911,382, water is used as a blowing agent, the water being provided in the form of a hydrated salt which decomposes at elevated temperatures to release water. US Patent No. 2,3
No. 86,995 teaches foaming vinyl esters and polystyrene with any suitable blowing agents and plasticizers, including water. Canadian Patent 84
No. 4,652 teaches the preparation of a foam-forming styrene-acrylic acid copolymer using water as a blowing agent. U.S. Pat. No. 4,278,767 teaches a flame retardant styrene copolymer foam produced by direct injection of water as a blowing agent. [0006] Finally, US Patent No. 4,455,272 teaches the formation of polystyrene foam using a blowing agent having a mixture of a volatile fluid blowing agent and water. Suitable volatile fluid blowing agents include propane, n-butane, isobutane, pentanes, hexanes, and halogenated hydrocarbons such as trichlorofluoromethane and dichlorodifluoromethane. The foam of US Pat. No. 4,455,272 has desirable physical properties and avoids the problems associated with the use of methyl chloride as a blowing agent. [0007] Nevertheless, the process taught by US Patent No. 4,455,272, and other patents that use water as a blowing agent, have proven to be inadequate in some respects. The amount of water suitable for use as a blowing agent is substantially limited to the amount of water that is soluble in the foam-forming polymeric material. When producing polystyrene foam, the amount of water that can be dissolved in polystyrene is small, and more importantly, less than the desired optimum. Inclusion of more water than dissolved in polystyrene leads to phase separation of water and polystyrene.
This phase separation results in a polystyrene foam product having unacceptable physical appearance and properties. [0008] To date, there is no known method of including water in polystyrene in an amount larger than that which is soluble in polystyrene. It would be desirable to find a method of producing a foam having an acceptable appearance and physical properties even with greater amounts of water than is soluble in polystyrene. [0009] Furthermore, the conventional method is highly filled (filled).
) Has proven to be inadequate when producing foam materials. this is,
This is because difficulties are encountered when extruding such highly filled materials. It is desirable to find a suitable method for producing a highly filled thermoplastic foam material. In addition, if the foam material is to be used as a thermal insulator, it is desirable to produce a foam having good structural strength and high thermal insulation value. SUMMARY OF THE INVENTION The present invention is directed to blending a mixture of a thermoplasticized polymeric material and a volatile organic fluid blowing agent at overpressure and elevated temperature and placing the resulting foamable mixture in a region of low pressure. extrusion, a process for the preparation of the alkenyl aromatic polymer foam having a density in the range of 16~80kg / m ^3, the volatile organic fluid foaming agent and a thermoplastic water-containing organic vegetable matter was pulverized with a predetermined amount A process for producing an alkenyl aromatic polymer foam, characterized in that it is included in a mixture of polymerized polymer materials. “Alkenyl aromatic polymer material” refers to a solid polymer of one or more polymerizable alkenyl aromatic compounds. The polymer or copolymer, in chemically bonded form, may comprise at least one of the following general formulas: Wherein Ar represents a benzene-based aromatic halohydrocarbon group or an aromatic hydrocarbon group, and R is hydrogen or a methyl group. Have. Typical of such alkenyl aromatic polymer materials are styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, ar-ethylstyrene, ar-vinylxylene, ar-chlorostyrene. Or a solid homopolymer of ar-bromostyrene; two or more such alkenyl aromatic compounds and a minor amount of other easily polymerizable olefinic compounds, such as methyl acrylonitrile methacrylate, maleic anhydride, It is a solid copolymer with citraconic anhydride, metaconic anhydride, acrylic acid, rubber-reinforced (natural or synthetic) styrene polymer and the like. [0014] The alkenyl aromatic polymer material of the present invention suitably has a weight average molecular weight of 100,000 to 350,000 as determined by gel permeation chromatography. When the alkenyl aromatic polymer material has a copolymer of styrene and acrylic acid, acrylic acid is contained in the copolymer in an amount of 0.5 to 0.5% based on the total weight of the copolymer.
It is present at 30% by weight, preferably 0.5-20% by weight. [0015] The method of the present invention uses at least two different blowing agents. One of the blowing agents is a finely divided hydrous organic plant, and the other is a volatile fluid blowing agent. Volatile fluid blowing agents suitable for use in the present invention are those well known in the art. Examples of such volatile fluid blowing agents are volatile fluid fluorocarbons and ethyl chloride boiling at a temperature of 100 ° C. or less. Volatile fluid fluorocarbons are particularly desirable in the practice of the present invention. Examples of volatile fluid fluorocarbons are perfluoromethane, chlorotrifluoromethane, dichlorodifluoromethane, trichlorofluoromethane, perfluoroethane, 1
-Chloro-1,1-difluoroethane, chloropentafluoroethane, dichlorotetrafluoroethane, trichlorotrifluoroethane, perfluoropropane, chloroheptafluoropropane, dichlorohexafluoropropane, perfluorobutane, chlorononafluorobutane, and perfluorocyclobutane. . A preferred volatile fluid fluorocarbon is dichlorodifluoromethane. In the practice of the present invention, the volatile fluid blowing agent is an alkenyl aromatic polymer material 1
Used in an amount of 1 to 30 parts per 00 parts. Preferably, the volatile fluid blowing agent is used in the practice of the present invention in an amount of 3 to 25 parts per 100 parts of alkenyl aromatic polymer material. Various materials are suitable for use as hydrated organic plant matter. Suitably, such materials are inexpensive and can be ground relatively finely. Examples of suitable hydrous organic botanicals are organic botanicals such as corn cobs, soybeans, potatoes, wood, rice, cotton, and the like. For reasons of cost, ease of handling and availability, corn cobs are a preferred hydrous organic plant material. Typically, the finely divided hydrated organic plant material is used in the practice of the present invention in an amount of 0.5 to 20% by weight, based on the total weight of the alkenyl aromatic polymer material. Preferably, the finely divided hydrated organic vegetable material is used in an amount of 1 to 15% by weight, based on the total weight of the alkenyl aromatic polymer material. The finely ground hydrous organic matter suitably contains water in an amount of from 1 to less than 100% by weight, preferably 3 to 30% by weight, based on the total weight of the finely divided hydrous organic matter. . The amount of finely divided hydrous organic plant present in the alkenyl aromatic polymer material depends on the amount of water contained in the organic plant. For example, as the water content of the finely ground hydrous organic plant increases, the amount of the organic plant that should be present in the alkenyl aromatic polymer material decreases. The converse is also true. The amount and water content of the finely ground hydrous organic plant matter is such that 0.1 to 4.5% by weight, preferably 0.25 to 4.0% by weight of water is added to the alkenyl aromatic polymer material. Is chosen. Suitably, the finely divided hydrated organic vegetable has a particle size ranging from 0.05 to 0.5 millimeters, preferably from 0.07 to 0.5 millimeters. Desirably, the hydrated filler comprises a plurality of closed non-gas containing gases.
-Interconnecting is present in an amount sufficient to provide a foam having foam cells forming the cells, as well as secondary cells present at the junction thereof. In the process of the present invention, the finely ground hydrated organic vegetable material is used in an amount sufficient to serve as an extrusion aid if extrusion is a problem due to the high packing of the alkenyl aromatic polymer foam. Existing. In a preferred embodiment of the present invention, the hydrous organic plant is comminuted corn cobs. In this preferred embodiment, the corn cob has a water content of 8% by weight, based on the total weight of the corn cob, a particle size of 0.15 millimeters, and 100 parts of the alkenyl aromatic polymer material. Added to the alkenyl aromatic polymer material in an amount of 10 parts. Usually, the preparation of the alkenyl aromatic polymer foam according to the present invention is substantially carried out by the method shown and described in US Pat. No. 2,669,751.
In this method, the alkenyl aromatic polymer material and the finely divided hydrous organic plant are fed into an extruder. In the extruder, the alkenyl aromatic polymer material is thermoplasticized and intimately mixed with the finely divided hydrous organic plant. In an extruder, the volatile fluid blowing agent is injected into a dense mixture of the thermoplasticized alkenyl aromatic polymer material and the finely divided hydrous organic plant. A mixture of the thermoplasticized alkenyl aromatic polymer material, the finely divided hydrated organic vegetable and the volatile fluid blowing agent exits the extruder and passes into a mixer. The mixer has studs that engage the studs on the rotor (stu
dded) A rotary mixer in which a studded rotor is housed in a housing having an inner surface. The mixture from the extruder is fed into the inlet end of the mixer and discharged from its outlet end. The flow is generally axial. From the mixer, the mixture is passed through a cooler, such as the cooler described in U.S. Pat. No. 2,669,751, and from the cooler is passed through a die to extrude a generally square slab. A generally similar and preferred extrusion system is disclosed in US Pat. No. 3,966,381.
No. As will be appreciated by those skilled in the art, many variations of the foregoing method are possible without departing from the spirit of the invention. For example, in some cases, it may be desirable to inject a small amount of unbound water into a mixture of finely divided hydrated organic botanicals together with a thermoplasticized alkenyl aromatic polymer material and a volatile fluid blowing agent. is there. Typically, the thermoplasticized alkenyl aromatic polymer material is heated to a temperature between 120 ° C. and 260 ° C.
It is preferably fed under superatmospheric pressure at a temperature between 160 ° and 245 ° C. to form a mixture with the volatile organic fluid blowing agent and the finely divided hydrated organic plant in a mixing and cooling zone or vessel. The resulting mixture is blended at elevated pressure and elevated temperature. The pressure used can vary from 30 lb / in ² (2067 kPa) to the limit of the equipment,
A pressure of from 00 to 2500 lb / in ² (2,756 to 17,225 kPa) is preferred. [0023] The temperature of the resulting foamable mixture is reduced to a temperature such that when the pressure on the mixture is reduced, a polymer foam of the desired quality is formed. The reduced temperature is generally between 60 ° C. and 1 ° C., just before the pressure is released by extruding the mixture into a region of low pressure.
It is in the range of 90C, preferably in the range of 90C to 170C. In making foams according to the present invention, it is often desirable to add a nucleating agent to reduce the size of the primary cells. Suitable nucleating agents include talc, calcium silicate, indico, and the like. Various other additives can also be used, such as, for example, flame retardant chemicals, stabilizers, and the like. The foam produced by the method of the present invention desirably has a plurality of gas-containing primary closed cells, said primary cells being formed from a plurality of walls and walls, wherein said walls are adjacent cells. Wall connection where the wall and a portion of the wall have secondary air bubbles formed therein. The primary bubbles are suitably from 0.05 to
It has a diameter of 3.0 mm, preferably 0.1-2.5 mm. Said secondary bubbles are suitably 5 to 35% of the diameter of the primary bubbles, preferably 15%.
It has a cell diameter in the range of ~ 25% in size. Furthermore, foam bodies produced by the process of the present invention has a density of ^{1~5lb / ft 3 (16~80kg / m} 3). In addition, foams made by the method of the present invention have improved structural strength and insulation value. In addition, the foam material is economical to manufacture. The following examples are illustrative only and are not intended to limit the scope of the invention as claimed in any way. I want to. In the following examples, all parts given are parts by weight unless otherwise indicated. EXAMPLE 1 A styrene polymer foam was placed in a 2.5 inch (6.35 cm) diameter extruder equipped with a rotary mixer similar to the arrangement disclosed in US Pat. No. 2,669,751. Manufactured. The effluent from the rotary mixer is fed to U.S. Pat.
702 was passed through a heat exchanger of the type shown. The effluent from the heat exchanger is then fed to a plurality of static mixers or inter-facias of the type shown in U.S. Pat. No. 3,583,678.
l surface generator). The output from the static mixer was passed through a slot die. The following formulation was used: 100 parts by weight of polystyrene having a weight average molecular weight of 200,000; 0.1 part of barium stearate per 100 parts of polystyrene; 1.2 parts of hexabromocyclododecane per 100 parts of polystyrene; polystyrene 0.15 parts per 100 parts of 10% phthalocyanine blue polystyrene concentrate; 8 parts dichlorodifluoromethane per 100 parts of polystyrene; and 5% by weight, based on the total weight of the extruded material, of Maumee, Ohio. Anderson Corn Cobb (Auder
A finely ground corn cob, commercially available under the trade name LITRE COB from Son Corn Cob Company. 132 ° C foaming temperature
Met. Styrene polymer foam is 200 pounds per hour (9 pounds per hour).
(0.6 kg). The foam had a cross section of 8 inches (20.34 cm) to 1 inch (2.54 cm) and a density of 2.19 lb / ft ³ (35.06 kg / m ³ ). Other physical properties of the foam are shown in Table 1. Example 2 The method of Example 1 was repeated. The foam produced was 2.35 lb / ft ³ (37.
62 kg / m ³ ). Other physical properties of the foam are shown in Table 1. Example 3 The method of Example 1 was repeated. The resulting foam is 2.70 lb / ft ³ (43.
22 kg / m ³ ). Other physical properties of the foam are shown in Table 1. Example 4 10% by weight, based on the total weight of the material to be extruded, of the aforementioned LITRE C
The general method of Example 1 was repeated, except that OB was included in the formulation. The foam produced had a density of 1.97 lb / ft ³ (31.54 kg / m ³ ). Other physical properties of the foam are shown in Table 1. Example 5 10% by weight, based on the total weight of the material to be extruded, of the aforementioned LITRE C
The general method of Example 1 was repeated, except that OB was included in the formulation. The resulting foam had a density of 2.09 lb / ft ³ (33.46 kg / m ³ ). Other physical properties of this polystyrene foam are shown in Table 1. [Table 1] As shown in Table 1, the polystyrene foams produced in Examples 1 to 5 have a density of 31.56 to 43.25 kg / m ³ , and further have a density of 0.37 to 0.
It has a primary bubble of size 67 mm. FIGS. 1 and 2 show schematic cross-sectional views and cross-sectional photographs. As shown in these figures, secondary bubbles having a size of 5 to 35% of the size of the primary bubbles are bubbles. It was confirmed that it was present in the film and also at the connection between adjacent bubble films. As is apparent from the above description, the present invention is capable of various modifications and alterations which may be particularly different from the above description and description.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic sectional view of a polystyrene foam according to the present invention having primary and secondary cell structures. FIG. 2 is a photograph instead of a drawing, showing a cross-sectional structure of a polystyrene foam obtained by the method of the present invention.

Claims (1)

Claims 1. Blend a mixture of a thermoplasticized polymeric material and a volatile organic fluid blowing agent at overpressure and high temperature and extrude the resulting foamable mixture into a region of low pressure. a manufacturing method of an alkenyl aromatic polymer foam having a density in the range of 16~80kg / m ^3, which is the volatile organic fluid foaming agent and the thermoplastic of the water-containing organic vegetable matter was pulverized with a predetermined amount A process for producing an alkenyl aromatic polymer foam, which is included in a mixture of polymer materials. 2. The method of claim 1, wherein said hydrous organic plant material is selected from the group consisting of corn cobs, soybeans, potatoes, wood, rice and cotton. 3. The method according to claim 2, wherein the hydrous organic plant material is finely ground corn cobs. 4. The method according to claim 1, wherein said hydrous organic plant contains 3 to 30% by weight of water, based on the total weight of the hydrous organic plant. 5. The method according to claim 1, wherein said hydrous organic plant is present in an amount of 0.5 to 20% by weight, based on the total weight of the alkenyl aromatic polymer material. 6. The method of claim 1 wherein a predetermined amount of water is added to the thermoplasticized polymeric material. 7. The method of claim 1 wherein said hydrous organic plant is present in said alkenyl aromatic polymer material in an amount sufficient to act as an extrusion aid.