JPH0432101B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to an in-mold foam molded article of vinylidene chloride resin having excellent heat resistance, and more specifically, to an in-mold foam molded article made of an amorphous vinylidene chloride resin having a high glass transition point as a base material. The present invention relates to a novel vinylidene chloride resin foam molded product, which is an in-mold foam molded product with improved thermal deformability and is suitable for a wide range of heat insulation and cushioning applications. [Prior Art] Synthetic resin foams having uniform, fine closed cells have conventionally been excellent in heat insulation and cushioning properties, and have been used for various purposes depending on the physical properties of the base resin. In recent years, research has focused on the functions of foams to improve the added value of synthetic resins.As a result, many synthetic resins can now be foamed, and foaming technology has made great progress. Among these, foams that take advantage of the high gas barrier properties and excellent flame retardant properties of vinylidene chloride resins are expected, but the reality is that they have not yet appeared. The reason for this is that vinylidene chloride-based resins are generally susceptible to thermal decomposition during the extrusion process because (1) the processing temperature at which the resin is melt-processed and the decomposition temperature at which the decomposition reaction proceeds are too close; . (2) The barrier properties of the resin are high, making it difficult to impregnate the resin with a foaming agent. (3) It is difficult to adjust the foaming conditions because the adhesiveness of the resin is highly dependent on temperature near the foaming temperature. etc., and it has been extremely difficult to obtain a highly foamed and uniform foam without causing thermal decomposition. Under these circumstances, Japanese Patent Application Laid-open No. 127333/1983,
and JP-A No. 60-125649 discloses a foam molded product in which a large number of expandable particles made of substantially amorphous vinylidene chloride resin and a large number of multicellular foam particles are fused together. is advocating. The technology disclosed in this publication makes it possible to create foams that take advantage of the properties of vinylidene chloride resins (e.g., flame retardancy, oil and chemical resistance, gas barrier properties, mechanical strength, etc.). This was an epoch-making product that realized a foam that could maintain its thermal conductivity (excellent heat insulation properties) over a long period of time. [Problems to be Solved by the Invention] However, in the above-mentioned prior art, a vinylidene chloride resin with a low glass transition point (Tg) was used as the base resin, so the foam obtained from it was not heated at ambient temperature. In some cases, the gas inside the bubbles expands or contracts, changing the dimensions of the foam.
Alternatively, this change may cause permanent deformation of the cell membrane that constitutes the foam. Particularly when the temperature is high, secondary expansion occurs due to the ambient temperature, and there is a major problem in that it is extremely susceptible to deformation. the result,
Despite the excellent heat insulating performance of the resulting foam, the range of uses for which it can be used is limited. [Means and effects for solving the problems] An object of the present invention is to provide a foam with improved heating dimensional stability of the conventional vinylidene chloride resin foam molding, and to It is an object of the present invention to provide a foam for a heat insulating material that can be used in a wide temperature range from low temperatures to low temperatures, and has expanded suitability for use. Furthermore, we can create foams that do not impair the properties of vinylidene base resins (e.g., gas barrier properties, flame retardance, chemical resistance, mechanical strength, etc.), such as those that maintain low thermal conductivity over a long period of time. It is an object of the present invention to provide a foam for a heat insulating material, which has excellent characteristics such as low dimensional change due to ambient temperature. Vinylidene chloride resins generally have lower thermal stability than other synthetic resins, are difficult to impregnate with blowing agents, and furthermore, the viscoelasticity of the resin changes rapidly near its softening and melting temperature. As mentioned above, the foaming processability is poor because of this. It is necessary to achieve the above object without these unfavorable characteristics being inferior to the level disclosed in JP-A-60-125649. As a result of intensive research under these circumstances, the present inventors found that vinylidene chloride was modified by introducing certain heat-resistant monomer units and monomer units copolymerizable with them into vinylidene chloride as a base resin. By employing the resin, we have been able to provide a heat-resistant vinylidene chloride resin in-mold foam molded product. That is, the above-mentioned object of the present invention is to produce an amorphous vinylidene chloride-based material comprising vinylidene chloride, N-substituted maleimide, and one or more vinyl monomers copolymerizable with these, and having a glass transition point of 85°C or higher. In-mold foaming of a heat-resistant vinylidene chloride resin, characterized by a foam formed by a large number of multicellular foamed particles made of a copolymer that are in close contact with each other and fused together. This can be achieved by employing a molded body. Hereinafter, the content of the present invention will be explained in detail. The gist of the present invention is to provide an amorphous material obtained by introducing into vinylidene chloride as a base resin, an N-substituted maleimide as a component capable of imparting a high glass transition point, and at least one vinyl monomer copolymerizable with the N-substituted maleimide. Adopting a multi-component copolymer of polyester resin, Adopting multicellular foamed particles whose closed cell ratio becomes 60% or more by impregnating the base resin with an organic volatile foaming agent and heating it. Furthermore, a volatile organic blowing agent is added to resin particles with uniform particle size distribution from (Tg-10)℃ to (Tg+20)℃.
The reason is that a method of contact impregnation is adopted at a temperature range of . The first necessity is to improve the heat deformation resistance of the base resin in order to increase the heating dimensional stability of the final product, the foam molded product, which is the basis of the present invention. It is. As shown in FIG. 1, the volume change rate ( It is clear that the dimensional stability at higher temperatures is given to the volume change rate (curve) of the foamed molded product made of vinylidene chloride resin disclosed in JP-A-58-125649. It is. In other words, it has been modified without impairing flame retardancy, which is one of the excellent properties of vinylidene chloride resin. In terms of the characteristic values of the base resin, the glass transition point at which the microbrown interlocking of molecules can maintain a frozen state and the limiting oxygen index as a measure of flame retardancy are as follows: 32%, and the values of 71° C. and 23% for the conventional technology, it is clear that the above-mentioned objective has been achieved. That is, in the present invention, in order to increase the glass transition point of the base resin without impairing the properties of the vinylidene chloride resin, it is understood that effective copolymerization of N-substituted maleimide with a small amount of components is important. In addition, the heating dimensional stability of the foam is 5% at 70℃.
The volume change rate can be suppressed to the following. Next, the necessity of will be described in relation to the purpose of use of the in-mold foam molded article of the present invention. The foam molded product of the present invention can be used for various purposes, among which it is possible to utilize the gas barrier property, which is a major feature of vinylidene chloride resin, to create a material with low thermal conductivity within the fine cells that make up the foam. Foams containing certain gases, especially fluorinated hydrocarbon gases, can maintain low thermal conductivity for long periods of time, and can be expected to be excellent heat insulating materials. for example,
When compared with conventionally commercially available extruded foamed polystyrene plates, the superiority of the vinylidene chloride resin in-mold foam molded product of the present invention is obvious, as seen in FIG. That is, in order to exhibit such excellent characteristics, it is a prerequisite that the gas within the bubbles does not easily permeate and diffuse into the surrounding atmosphere.
In other words, the fine cells constituting the foam need to be closed cells separated by partition walls having high gas barrier properties between adjacent cells. In order to make such an in-mold foam molded product possible, it is necessary that the raw material, the multicellular foamed particles, has a high closed cell ratio. If the closed cell ratio of the multicellular foam particles is low, the resulting foamed molded product will not only have low heat insulation performance, but also the multicellular foam particles will expand when heated in the mold. When the interparticle voids are filled and fused together, mold reproducibility with the mold is poor and sink marks and shrinkage are likely to occur. In severe cases, a foamed molded product cannot be obtained. From this point of view, the closed cell ratio of multicellular foam particles is at least
60% or more is preferable. In order to provide even better heat insulation performance, it is more preferable to set it to 80% or more. Furthermore, the term "cellular" in the foamed foamed particles used in the present invention means that at least several fine air bubbles are present in the foamed beads. Since the particle diameter of the multicellular expanded particles is usually 0.2 to 5 mm, the cell diameter is preferably in the range of 0.01 to 1.0 mm. Next, the necessity of will be explained in relation to the method for producing expandable resin particles. As in the present invention, the base resin into which the heat-resistant monomer unit is introduced inevitably has a reduced solubility of the blowing agent, and therefore it is necessary to contact and impregnate the blowing agent at as high a temperature as possible. However, pinylidene chloride resins are generally easily thermally decomposable, and the base resin of the present invention cannot escape this property. Therefore, if left in a high-temperature atmosphere for a long time, the dehydrochloride reaction will proceed and the base resin will deteriorate. Causes heat denaturation. As a result, the foaming ability of the resin impregnated with the foaming agent is significantly reduced,
Furthermore, there are other problems such as deterioration of the physical properties of the foam molded product. In addition, hydrochloric acid and chlorine generated by thermal decomposition of the resin cause corrosion of equipment such as pressure containers, which poses a major problem in terms of manufacturing safety. As mentioned above, it is necessary to impregnate the base resin with a foaming agent that has sufficient foaming ability while balancing various problems. The present inventors adjusted the particle diameter of the base resin particles to a range of 0.1 mm to 1.0 mm or less, and set the impregnation temperature T of the blowing agent to a range expressed by the following formula based on the glass transition temperature Tg of the base resin. The above objective was achieved by selecting among the following. (Tg-10)°C≦T≦(Tg+20)°C Figure 3 shows vinylidene chloride resin particles of the present invention having various particle sizes, exposed to contact impregnation at 100°C in a blowing agent solution for 70 hours. The amount of blowing agent contained in the resin particles (curve) immediately after impregnation and the amount of blowing agent contained in the particles after leaving it open under atmospheric pressure at 32°C for 8 days (curve). As is clear from these results, the impregnation rate of the blowing agent largely depends on the diameter of the resin particles. The smaller the particle size, the easier it is to impregnate, and there is a linear correlation with the particle size.
Particles with a particle diameter of less than 0.1 mm or more than 1 mm deviate greatly from linearity. In addition, regarding the retention of the foaming agent, the smaller the particle size of the resin, the easier it is to escape.
It is clear that a linear relationship is not necessarily obtained, and that there is significant foaming agent escape with resin particles smaller than 0.1 mm. Therefore, the particle diameter of the resin particles is preferably 0.1 to 1.0 mm, more preferably 0.2 mm to 0.6 mm. Furthermore, if the particle size distribution of the base resin particles is uneven, the expansion ratio distribution of the resulting multicellular foam particles will also be uneven, and if the particles are subjected to in-mold foam molding, local density changes will occur. This results in only uneven foam molded products being obtained. Therefore, it is preferable that the particle size distribution of the base resin particles is uniform. Furthermore, Figure 4 shows the expansion ratio when the expandable resin particles, which were adjusted to contain the same amount of blowing agent by changing the impregnation temperature of the blowing agent, were subjected to primary foaming under constant heating conditions. This is the result of plotting against processing temperature. Glass transition point of base resin +20℃
It is clear that the foaming ratio rapidly decreases when the value exceeds . This is thought to be because, as mentioned above, the impregnation treatment caused thermal denaturation of the base resin, resulting in a large change in viscoelasticity at the heating and foaming temperature. To achieve the purpose of the present invention, the impregnation temperature of the blowing agent must not exceed the Tg of the base resin + 20°C. Also,
When impregnating a blowing agent at a low temperature, it takes a long time to impregnate the required amount of blowing agent. The impregnation temperature of the blowing agent is preferably in the range of (Tg-10)°C to (Tg+20)°C. Of course, the impregnation time of the blowing agent is appropriately selected depending on the impregnation temperature and the desired expansion ratio. Usually within 200 hours,
Preferably it is selected within 100 hours. N-substituted maleimide is selected as the main component for increasing the glass transition point of the modified vinylidene chloride resin used in the present invention. Examples of the N-substituted maleimide include N-methylmaleimide, N-ethylmaleimide, N-propylmaleimide, N-butylmaleimide, N-cyclohexylmaleimide, N-phenylmaleimide, N-2
-methylphenylmaleimide, N-2-ethylphenylmaleimide, N-2-chlorophenylmaleimide, N-2-methoxyphenylmaleimide,
Examples include N-2,6-dimethylphenanylmaleimide, and one or more of these can be used. N-phenylmaleimide and N-2-chlorophenylmaleimide are preferred because they are industrially easily available, and N-phenylmaleimide is particularly preferred. Vinylidene chloride and one or more vinyl monomers copolymerizable with the above N-substituted maleimide include vinyl chloride, acrylonitrile, methacrylonitrile, styrene, α-methylstyrene, vinyl acetate, acrylic acid, methacrylic acid, methyl acrylate, These include ethyl acrylate, butyl acrylate, methyl methacrylate, glycidyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, hydroxyethyl acrylate, glycidyl methacrylate, and one or more of these can be used. acrylonitrile, styrene,
Methyl methacrylate is preferred because it can easily raise the glass transition point of the copolymer composition. Further, acrylonitrile is preferable from the viewpoint of imparting flame retardancy, but it is even more preferable to use a mixture of acrylonitrile and styrene because the thermoplasticity and elongation at high temperatures of the copolymer composition will be increased. The monomer composition of the amorphous multi-component copolymer includes 30 mol% to 65 mol% of vinylidene chloride, N-
1 mol% to 10 mol% of substituted maleimide and 25 mol% of one or more monomers copolymerizable with these
Preferably, a composition range of ~70 mol% is chosen. If the amount of vinylidene chloride is less than 30 mol%, the resulting foamed molded article will have insufficient flame retardancy, and if it exceeds 65 mol%, impregnation with the blowing agent will be poor. In addition, if the content of N-substituted maleimide is less than 1 mol%, the glass transition point of the base resin will be low, resulting in inferior heating dimensional stability of the resulting foam molded product, and if it exceeds 10 mol%, impregnation of the blowing agent will occur. Sexuality becomes poor. Further, as a crosslinking component, one or more compounds having two double bonds in one molecule represented by the general formula () may be used in an amount of 0 to 0.1 mol%. [R ₁ represents -H or -CH ₃ , R ₃ is

[Reference example]

A reaction vessel is charged with 150 parts of water and 0.2 parts of hydroxypropyl methylcellulose as a suspending agent. There, as monomers, 50 parts of vinylidene chloride (41.1 mol%), 5 parts of N-phenylmaleimide (2.4 mol%),
30 parts of acrylonitrile (45.1 mol%), styrene
15 parts (11.4 mol %) and 0.6 parts of lauryl peroxide as a radical polymerization initiator are added. After replacing with nitrogen, start stirring and react at 60°C for 24 hours. After the polymerization is completed, the resulting polymer is separated and dried. Processed to reduce residual monomer to 0.2% or less. The polymerization rate was 98%. Weight average molecular weight was determined by gel permeation chromatography analysis method.
It was 299,000. Glass transition point is ASTM D3418
-75, the temperature was determined to be 96°C by differential calorimetry.
The critical oxygen index was 32% according to JIS-K7201. In addition, the amorphous polymer as used in the present invention refers to a polymer that does not exhibit an endothermic peak due to melting of crystalline components when measured using a differential scanning calorimeter (DSC), and
It does not show any diffraction peaks based on crystalline components determined by line diffraction. Generally vinylidene chloride is 85
Although the copolymer becomes crystalline in a region larger than mol%, these crystalline copolymers are excluded from the scope of the present invention. As the blowing agent that can be used in the expandable resin particles of the present invention, a volatile organic blowing agent having a boiling point lower than the glass transition point of the resin used is used. The blowing agent is determined by considering the solubility in the resin, the vapor pressure at the foaming temperature, the boiling point of the blowing agent, etc., but in particular, use a blowing agent with a molar average solubility coefficient (SP value) in the range of 5.7 to 7.0. is preferred. Specifically, for example, aliphatic hydrocarbons such as propane (6.4), butane (6.8), isobutane (6.8), pentane (7.0), isopentane (6.7), neopentane (6.3), methyl chloride (9.7), Chlorinated hydrocarbons such as ethyl chloride (9.2), methylene chloride (9.7), trichloromonofluoromethane (7.6), dichlorodifluoromethane (5.5), dichloromonofluoromethane (8.3), monochlorodifluoromethane (6.5), trichlorotrifluoromethane Examples include fluorinated hydrogens such as fluoroethane (7.3), dichlorotetrafluoroethane (6.2), monochlorodifluoroethane (6.8), and difluoroethane (7.0), and ether acids such as dimethyl ether (7.6) and methyl ethyl ether (7.6). and chosen from among these. Of course, if one type of foaming agent does not satisfy the above objectives, it is preferable to mix two or more types of foaming agents and select a foaming agent suitable for foaming the resin. The solubility coefficients (SP values) shown in parentheses are based on the Polymer Handbook, 2nd edition, G.I. Brandlap and E.H. Immergat.
Hand Book Second Edition, J.BRANDRUP
and EHIMMERGUT) (published in 1974). In cases where the values were not described in the above literature, values from other literatures were used, or values at 25°C calculated using the formula below were used. (SP value) ² = d/M (ΔH-RT) d: Density g/cc M: Molecular weight g/mol △H: Evaporation latent cal/mol R: Gas constant cal/mol・〓 T: Absolute temperature 〓 Mixing In the case of blowing agents, the molar average solubility coefficient, which is the sum of the products of the SP value of each component and its molar fraction, is used. Among these blowing agents, fluorinated hydrocarbon blowing agents are preferred in order to maintain low thermal conductivity over a long period of time, which is one of the objectives of the present invention. When a fluorinated hydrocarbon-based mixed blowing agent is used, combined with the gas barrier properties of the resin, the blowing agent resin particles retain their foaming ability significantly, and the molded product after becoming a foam exhibits It has excellent insulation performance and maintains its performance over a long period of time. Methods for incorporating the blowing agent into the resin include a gas phase or liquid phase impregnation method in which resin particles are impregnated with the blowing agent in gas or liquid form under heating and pressure if necessary in an autoclave; There is a suspension impregnation method in which the foam is suspended in water and impregnated with a foaming agent. The polymerization can also be carried out in the presence of a blowing agent to directly obtain expandable polymer particles. The foaming agent used in the present invention can be generally used in an amount of 1 to 40 parts by weight per 100 parts by weight of the resin particles, and the amount used is adjusted depending on the target density of the foam. Preferably 5 to 30 parts by weight are used. As a foaming method for obtaining the multicellular foam particles of the present invention, for example, a known method is used in which resin particles containing a foaming agent are heated and foamed with a heating medium such as steam, hot water, or hot air. be able to. Therefore, the viscoelastic behavior of the foaming agent and resin mixture in a heated fluidized state greatly influences the closed cell ratio of the resulting multicellular expanded particles. If the elastic modulus is too high, it is difficult to obtain a foam with a high magnification or a foam with a uniform fine cell structure, and if viscous flow is predominant, it is difficult to obtain a closed cell. Among the base resins of the present invention, the glass transition point (Tg) of the resin or higher or (Tg +
In order to obtain a high-strength foam with a closed cell ratio of 60% or more, it is preferable to select a resin having a tensile elongation of at least 200% in a temperature range of 50)°C or lower. The closed cell ratio here is measured with an air comparison type hydrometer, and indicates the ratio of closed cells in the foam to the previous cells. As heating conditions for obtaining multicellular expanded particles, heating for a predetermined time at a temperature equal to or higher than the glass transition point (Tg) of the base resin is appropriately selected depending on the desired magnification. Generally the temperature range is 100-130℃, 5
A heating time of ~180 seconds is sufficient. The in-mold foam molded article of the present invention is obtained by applying a known in-mold molding method to the multicellular foam particles obtained as described above. That is, a mold with many small holes that can be closed but cannot be sealed is filled with porous foam particles, and the foam is expanded by heating with a fluid such as steam through the small holes from outside the mold wall. is formed, the interparticle voids are filled and fused, and then this is rapidly cooled to form a molded body. Through this manufacturing method, a large number of multicellular foamed particles whose base resin is heat deformation-resistant vinylidene chloride resin are fused together by closely contacting the outer surfaces of adjacent particles to form an integrated foamed molded product. The structure is as follows. Specifically, the heating conditions can be almost the same as those for the well-known in-mold molding method for foamed polystyrene particles, and are appropriately set depending on the shape and wall thickness of the molded product. Generally mold heating (0
Kg/cm ² -G water vapor), while heating (0.1 to 0.5 Kg/
cm ² -G steam), and double-sided heating (0.7 to 2.0 Kg/
An ^integral molded body is obtained by the step of cooling the mold with cold water. The density of these foams can be changed depending on the requirements of each application, since the mechanical strength required varies depending on the application. In the present invention, the expansion ratio can be controlled by the impregnated amount of the blowing agent, the heating temperature and time when obtaining multicellular foam particles, and the in-mold foam molded product can have a density of 15 to 300 Kg/m ³ can be handled. Further, in order to achieve excellent heat insulation performance, which is a major feature of the present invention, it is preferable to minimize the diffusion and permeation of the gaseous foaming agent trapped in the bubbles into the atmosphere. That is, it is preferable that the aging conditions from heating the expandable resin particles to obtain the foamed particles to forming the in-mold moldings are short. Generally, room temperature can be maintained within 24 hours, particularly preferably within 1 hour. Of course, this is not the case if it is used for purposes other than heat insulation, and it can be handled in the same way as expanded polystyrene particles, and for example, it is acceptable even if it requires a maturing period of about one week. [Effects of the Invention] The amorphous vinylidene chloride resin in-mold foam molded article of the present invention has excellent characteristics of the base resin, such as gas barrier properties, resistance to oxidation, mechanical strength, etc. In addition, the present invention provides a foam that takes advantage of a high glass transition point (Tg) that has not been possible before. In other words, it is self-extinguishing, can maintain low thermal conductivity for a long period of time, and is
Alternatively, the present invention provides a novel in-mold foam that has excellent dimensional stability at low temperatures and can be applied to various industrial applications. As described above, the present invention is an extremely useful invention industrially. [Example] Hereinafter, the present invention will be explained in detail with reference to Examples. The evaluation method used in the present invention is as follows. Γ Foam density: Based on JIS K-6767. Γ Foaming ratio: Base resin density divided by foam density. Γ Closed cell ratio: Based on ASTM D-2856. Γ Thermal conductivity: Based on ASTM C-518. Γ Average cell diameter: The air diameter in an arbitrary cross section of the foam was measured at 5 to 10 points, and the arithmetic mean value was used. Γ5% compressive strength: Based on ASTM D-1621, the amount of compressive strain is 5%. Γ Limit oxygen index: Based on JIS K-7201. Γ Glass transition point: Measure the exothermic or endothermic differential curve from the differential calorific value vs. temperature function using a differential scanning calorimeter (DSC) according to ASTM D-3418-75. Examples/Comparative Example 1 Vinylidene chloride (42
mol%), N-phenylmaleimide (2.4 mol%),
With monomer composition ratio of acrylonitrile (44.3 mol%) and styrene (11.3 mol%), resin 100
Copolymer resin particles crosslinked with 0.02 parts by weight of divinylbenzene were used in experiments. The specific gravity of the resin is 1.49 and the glass transition point is 96℃
It was hot. 100 parts by weight of the resin particles having an average particle diameter of 0.4 mm are placed in an autoclave, and the autoclave is sealed and degassed under vacuum.
Next, Freon 11 and Freon 22 are 90:10.
300 parts by weight of a liquid mixed blowing agent with a weight ratio of . After being kept under stirring at 100°C for about 70 hours, the mixture is cooled to room temperature, returned to normal pressure, and the particles inside are taken out. The particles were impregnated with about 19 parts by weight of blowing agent. After impregnating the foamable resin particles with a foaming agent 2
After being left open indoors for a week, 0.5Kg/cm ²
- Heat and foam with G steam for 20 seconds, foaming ratio 24
twice as many pre-expanded particles were obtained. The obtained expanded particles are
The average particle diameter was about 1.2 mm, the average cell diameter was 0.1 mm, and the closed cell ratio was 95%. Next, the pre-expanded particles with an expansion ratio of 24 times are heated with steam of about 1.1 kg/cm ² -G in an in-mold steam molding machine for expandable polystyrene within 30 minutes immediately after foaming, and are in-mold molded. A foamed flat plate molded product having a thickness of 25 mm, a square shape of 300 mm, and a density of 40 Kg/m ³ was obtained. The obtained molded product was cut into a size of 100 x 100 x 25 mm and heat treated at a predetermined temperature for 24 hours, and the dimensional change was read and the volume change rate was measured. The results are shown in Figure 1. Also, the 5% compressive strength is 2.0
It was Kg/ ^cm2 . In addition, Fig. 2 shows the results of tracing the change in thermal conductivity over time of the flat plate having a density of 40 kg/m ³ . For comparison, we also show that of a polystyrene extrusion foam liquid, which is said to have excellent thermal conductivity. According to Example 1 of JP-A-60-125649,
Vinylidene chloride and methyl methacrylate 60/40
An in-mold foam molded article consisting of the copolymer was obtained. The glass transition point of the base resin is 71°C. The obtained molded body was cut into 100 x 100 x 25 mm,
The volume change rate after heating was measured in the same manner as in Example 1, and the results are shown in FIG. As is clear from FIG. 1, it can be seen that the heating dimensional stability of the conventional vinylidene chloride resin foam is greatly improved by using the base resin of the present invention. Examples/Example 2 The particle diameter of the base resin is 0.08, 0.1, 0.2, 0.4, 0.6,
Foaming agent-impregnated resin particles were obtained in the same manner as in Example 1 except that the diameters were 0.8, 1.0, and 1.2 mm. The amount of blowing agent contained in the expandable resin particles thus obtained was measured immediately after impregnation (curve) and after being left open for 8 days at 32° C. under normal pressure. The results are shown in FIG. As is clear from the figure, when the particle size of the base resin exceeds 1 mm, the impregnation of the blowing agent is significantly reduced. Furthermore, it can be seen that when the particle size is less than 0.1 mm, the blowing agent escapes significantly due to changes over time. Example/Comparative Example 3 Base resin particles and a blowing agent were placed in an autoclave in the same manner as in Example 1, and the blowing agent impregnation temperature and time were adjusted as shown in Table 1 to obtain a predetermined amount of blowing agent. Expandable resin particles impregnated with
Similarly, the amount of blowing agent contained in each particle was
Shown in the table. These resin particles were left open at room temperature for two weeks, and then heated and foamed with steam at 1.0 kg/cm ² -G for 30 seconds to obtain pre-expanded particles. The cell diameter, closed cell ratio, and expansion ratio of the obtained expanded particles are also shown in Table 1. In addition, the correlation between the expansion ratio and the impregnation temperature conditions is shown in FIG. As is clear from this figure, when the impregnation temperature was 130°C, the foaming ability was significantly reduced. This is because the base resin exposed to the high temperature conditions of 130°C undergoes a thermal decomposition reaction, which significantly changes the original properties of the resin. Therefore, the impregnation temperature of the blowing agent must be 115°C or lower, that is, Tg of the base resin (=96°C) + 20°C or lower. Further, the pre-expanded particles obtained in this example were aged indoors for one day, and then molded in an in-mold molding machine for expandable polystyrene to obtain a molded product having a thickness of 25 mm and a size of 300 mm square. At that time, the steam pressure necessary to fuse the pre-expanded particles in close contact with each other without any voids, the density of the obtained molded product, and its 5% compressive strength are also summarized in Table 1. show. As is clear from the above, the blowing agent impregnation condition of 130° C. requires a steam pressure exceeding the equipment pressure (approximately 1.5 kg/cm ² ) of the in-mold molding machine for expandable polystyrene, which is not preferable. On the other hand, if the impregnation temperature of the blowing agent is too low, an extremely long time is required to impregnate the desired blowing agent, which is not preferable. as an acceptable temperature
The temperature is preferably 85°C, that is, Tg of the base resin - 10°C or higher. Example/Comparative Example 4 The molar ratio of vinylidene chloride (VDC), N-phenylmaleimide (N-PMI), acrylonitrile (AN), and styrene (St) is as shown in Table 2, and the crosslinking agent Divinylbenzene (DVB) was added to 100 parts by weight of the resin, and the weight ratio of Freon 11 and ethylene chloride was 90:10 to base resin particles with a particle diameter of 0.5 mm, which were also adjusted as shown in Table 2. A mixed blowing agent was impregnated in the same manner as in Example 1. The amount of blowing agent impregnated was adjusted by changing the impregnation time as shown in Table 2. After leaving the foamable resin particles indoors for 2 weeks, 0.5Kg/cm ² -G
The mixture was heated and foamed with steam for 30 seconds to obtain pre-expanded particles. The expansion ratio, closed cell ratio, and
The particle sizes are shown in Table 2. Furthermore, after aging these expanded particles indoors for one day, in-mold molded products were obtained, and Table 2 shows the density and volume change rate after heating at 70° C. for 24 hours. Next, as a comparison, a copolymer of vinylidene chloride (VCD) and acrylonitrile (AN), vinylidene chloride (VDC), acrylonitrile (AN),
Also for the copolymer with methacrylonitrile (MAN), the particle size of the composition shown in Table 2 is 0.5 mm.
The resin particles were impregnated with a foaming agent mixture containing Freon-11 and ethylene chloride in a weight ratio of 90:10 in the same manner as in Example 4 to obtain expandable resin particles. Pre-expanded particles and in-mold foam molded articles were similarly obtained for these, and the results of evaluation for each are shown in Table 2. For Experiment Nos. 9, 10, and 11 in Table 2, the tensile elongation degree of the base resin at (Tg+25)°C is also shown. Resin No. 10 had an extremely low tensile elongation of 50% during heating, and the closed cell ratio of the pre-expanded particles was 35%. On the other hand, No.9,
The tensile elongation of the 11 resins is 380% and 680%, respectively, and the closed cell ratio of the expanded particles is 60% and 72%. The higher the degree of tensile stretching of the resin, the higher the closed cell ratio of the resulting foam tends to be. However, the pre-expanded particles obtained from resin No. 11 have the disadvantage that, although the cause is unknown, the cell diameter is large compared to the particle size, making it difficult to obtain porous particles.

【table】

【table】

【table】 [Brief explanation of drawings]

Figure 1 shows the relationship between the heating temperature and volume change rate of the foam molded product of the present invention in comparison with that of the foam molded product disclosed in known patent publications. Figure 3 shows the change in conductivity over time in comparison with an extruded foamed polystyrene plate. Figure 3 shows the relationship between the resin particle diameter and the amount of blowing agent contained in the foam molded product of the present invention, immediately after impregnation and after impregnation. FIG. 4 is a diagram showing the relationship between the blowing agent impregnation temperature and the foaming ratio at the same impregnating amount.

Claims (1)

[Scope of Claims] 1. An amorphous vinylidene chloride copolymer comprising vinylidene chloride, N-substituted maleimide, and one or more vinyl monomers copolymerizable with these, and having a glass transition point of 85°C or higher. A heat-resistant polyvinylidene chloride resin in-mold foam molded product, characterized in that a large number of multicellular foamed particles formed by coalescence are in close contact with each other and fused to form a foam. . 2. The vinylidene chloride resin in-mold foam molded product according to claim 1, wherein the foam molded product has a density of 15 to 300 Kg/m ³ . . 3. The vinylidene chloride-based resin in-mold foamed molded product according to claim 1, wherein the polycellular foam particles are made of a vinylidene chloride-based resin and have a closed cell ratio of 60% or more. 4. The vinylidene chloride resin in-mold foamed product according to claim 1, wherein the foamed molded product has a volume change rate of 5% or less when heated at 70°C. Foam molded body. 5 The amorphous vinylidene chloride copolymer contains 30 mol% to 65 mol% vinylidene chloride, 1 mol% to 10 mol% N-substituted maleimide, and one or more vinyl monomers copolymerizable with these. is 25 mol% ~
The vinylidene chloride resin in-mold foam molded article according to claim 1, characterized in that the polyvinylidene chloride-based resin resin contains 70 mol%.