JPS6245257B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention includes a thermoplastic synthetic resin containing at least 0.1 to 10% of a compound having the effect of suppressing the escape of blowing agent gas from the foam, improving the gas efficiency of the blowing agent, and preventing significant shrinkage of the foam. The present invention relates to a synthetic resin composition for foaming containing % by weight. Generally, thermoplastic resin foams are manufactured by gasifying the blowing agent by adding a blowing agent to the resin and heating it, but improving the gas efficiency of the blowing agent is economically important in industrial production. It has great significance. On the other hand, among thermoplastic resins, polyolefin resins in particular are considered difficult to be industrially foamed as they are. The reason for this is that when polyolefin resin is melt-processed, its thermo-hydraulic and viscoelastic properties are highly dependent on temperature, and the cell membrane of the resin itself is highly permeable to gas, reducing the gas pressure required for foaming. It is thought that this is because it is difficult to hold the foam in the bubbles, and it is said that this is because these factors have a complex influence on the expansion heat absorption, crystallization heat, etc. that occur during foaming, making it difficult to set the foaming conditions. Therefore, when foaming polyolefin resins, especially when the expansion ratio is 5 times or more, it is necessary to crosslink and modify the resin, or to modify the resin by mixing it with other resins. It is considered common sense to do this. However, as an exception, Special Publication No. 35-4341 states,
There is a disclosure of a technique for extruding and foaming a non-crosslinked polyolefin resin. However, this method
It has the drawback that it can be achieved only with a special and expensive blowing agent such as 1,2-dichlorotetrafluoroethane, which impairs economic efficiency.In addition, the resulting molded product gradually shrinks immediately after molding and deteriorates over time. Either the dimensions do not recover and it becomes impossible to obtain a molded product with the target density, or even if the dimensions recover, the time required for recovery becomes extremely long, leaving wrinkles on the surface of the molded product and deteriorating its appearance. However, there are disadvantages in that the quality of the molded product deteriorates and the problems in dimensional control have not yet been solved. The present invention was made in view of the current situation, and its purpose is to economically produce thermoplastic resin foams, and to foam polyolefin resins, especially non-crosslinked polyolefin resins, using common foaming agents. Molding can be easily performed, and the molded product obtained has almost no shrinkage over time, and has good dimensional stability and
It is an object of the present invention to provide a thermoplastic synthetic resin composition for foaming, from which a foamed molded article with excellent surface smoothness can be obtained. The present invention relates to compounds represented by the general formula [], [] [In the formula, R ₁ is an aliphatic hydrocarbon group having 11 to 24 carbon atoms,
or an aliphatic carboxylic acid residue, _R2 is an aliphatic polyhydric alcohol residue having 1 to 5 carbon atoms, _R3 is an aliphatic dicarboxylic acid residue having 2 to 14 carbon atoms, and n is a positive integer from 0 to 100, and m is 1 or 2. ] Provided is a foamable thermoplastic synthetic resin composition containing one or more of the following. The effects of the compounds represented by the general formulas [] and [] in the present invention can be seen from the comparison of volume changes and weight changes of the foam shown in Figures 1 and 2, respectively. This is thought to be because it suppresses the escape of foaming gas. It has not been previously known that the permeation of foaming gas can be suppressed by adding a compound represented by the general formula [] or [] to a resin, and this is a new finding. In the compounds of general formulas [] and [], which are requirements of the present invention, R ₁ is an aliphatic hydrocarbon group having 11 to 24 carbon atoms or an aliphatic carboxylic acid residue, such as undecanoic acid, lauric acid, palmitic acid,
These are residues of stearic acid, oleic acid, behenic acid, lignoceric acid, erucic acid, etc., mixed fatty acids of these produced from natural oils and fats, and alcohols obtained by reducing these fatty acids. These aliphatic groups are preferably saturated hydrocarbons, but may also contain partially unsaturated hydrocarbons. R ₂ is an aliphatic polyhydric alcohol residue having 1 to 5 carbon atoms, such as methylene, ethylene, trimethylene, tetramethylene groups (including isomers), and these polyglycol residues, such as polyethylene Glycol, polypropylene glycol, polytetramethylene glycol residues. Also, polyhydric alcohols having 3 to 5 carbon atoms, for example,
These are residues of glycerin, erythritol, pentaerythritol, arabite, etc. Alternatively, a mixture of these may be used. R ₃ is an aliphatic dicarboxylic acid residue having 2 to 14 carbon atoms, such as oxalic acid, malonic acid, cis-maleic acid, succinic acid, glutaric acid, adipic acid,
These are residues of azelaic acid, sebacic acid, dodecamethylene dioic acid, etc. Among these, aliphatic dicarboxylic acids having 2 to 6 carbon atoms are particularly useful for the purpose of the present invention. n is a positive integer from 0 to 100, and R ₁ , R ₂ ,
The optimal range of R ₃ differs depending on the number of carbon atoms, but
For example, R ₁ has 16 to 22 carbon atoms, R ₂ has 2 carbon atoms,
When the number of carbon atoms in R ₃ is 4 and m=2, the range is preferably from 0 to 10. Typical compounds represented by the general formula [] are, for example, mono(di)lauryl malonic acid ester, mono(di) palmityl malonic acid ester, mono(di)
Stearyl malonic acid ester, mono(di)behenyl malonic acid ester, mono(di)(palmityl polyoxyethylene) malonic acid ester, mono(di)(stearyl polyoxyethylene) malonic acid ester, mono(di)(palmityl) oxyethylene) malonic acid ester, mono(di)(stearyloxyethylene) malonic acid ester, mono(di)
lauryl adipate, mono(di)palmityl adipate, etc. Typical compounds represented by the general formula [ ] include mono(di) laurylamide malonic acid amide, mono(di)palmityl adipate, etc. Mitylamide malonic acid amide, mono(di)stearylamide malonic acid amide, mono(di)behenylmalonic acid amide, mono(di)(palmitylamide polyoxyethylene) malonic acid ester, mono(di)(stearylamide polyoxy) Ethylene) malonic acid ester, mono (di) (palmitylamide oxyethylene) malonic acid ester, mono (di) (stearylamide oxyethylene) malonic acid ester, mono (di) laurylamide adipic acid amide, mono (di) These include palmitylamide adipic acid amide and the like. The amount of compounds represented by the general formulas [] and [] of the present invention is at least one of the compounds represented by the general formulas [] and [] based on the resin.
It is necessary to contain 0.1% by weight and keep the total amount in the range of 0.1 to 10% by weight. The amount added can be arbitrarily selected within the above range depending on the resin used, the blowing agent, the shape properties (density, mechanical properties, etc.) of the foam, etc., but is generally preferably in the range of 0.3 to 7% by weight.
If the amount added is less than 0.1% by weight, the appearance (wrinkles, shrinkage) of the foam will be significantly reduced, making it impossible to obtain a good foam. Moreover, the physical properties of the resulting foam are also deteriorated. On the other hand, if it is added in an amount exceeding 10% by weight, the effect of the present invention will no longer be improved and it will be economically disadvantageous, and on the contrary, it will exhibit a plasticizing effect and may deteriorate the properties of the foam, which is not preferable. The thermoplastic resin in the composition of the present invention includes:
These include polystyrene, styrene copolymers of styrene and other copolymerizable monomers, and polyolefin resins. Polyolefin resins include polyolefin resins containing olefin as a main component, such as low density polyethylene, medium and high density polyethylene. density polyethylene, isotactic polypropylene,
Polybutene-1, copolymers of ethylene or propylene with other copolymerizable monomers, such as propylene-octene-1-ethylene copolymers, ethylene-propylene copolymers, ethylene-vinyl acetate copolymers, ethylene-vinyl acetate copolymers, Acrylic acid copolymer, ethylene-ethyl acrylate copolymer, ethylene-vinyl chloride copolymer, and ethylene-acrylic acid copolymer zinc, sodium, calcium,
There are magnesium salts, etc. These resins may be used alone or in combination. The compound of the present invention can be incorporated into the resin by heating and kneading with a kneader such as a single-screw extruder, twin-screw extruder, roll, or Banbury mixer. Further, as the method of addition, dry blending, masterbatch method, melt injection method, etc. can be used. A known method can be used to obtain a foam using the composition of the present invention. For example, the resin composition of the present invention may be heated and melted, a blowing agent may be mixed and melted at high temperature and under high pressure, and the foam may be extruded into a low pressure zone, or the blowing agent may be added to the resin composition under high temperature and high pressure, and the pressure may be removed. batch method of foaming,
A method of crosslinking a resin composition with an electron beam or a chemical crosslinking agent, adding a foaming agent thereto, and heating and foaming it;
etc. are selected according to the purpose. Among these, the effects of the present invention are particularly remarkable in the method of manufacturing a highly foamed body with a foaming ratio of 5 times or more by the extrusion foaming method. The blowing agents used in producing the foam are common chemical blowing agents and volatile organic blowing agents. Particularly preferred are volatile organic blowing agents, and any blowing agent that boils below the melting point of the thermoplastic resin may be used. Representative hydrocarbons include propane, butane, pentane, pentene, hexane, hexene, heptane, octane, and the like. Further, there are halogenated hydrocarbons that satisfy the same restriction regarding boiling point, and examples of halogenated hydrocarbons that can be used include methylene chloride, trichlorofluoromethane, dichlorofluoromethane, chlorodifluoromethane, chlorotrifluoromethane, These include dichlorodifluoromethane, 1,1'-dichloroethane, 1-chloro-1,1'-difluoroethane, 1,2-dichlorotetrafluoroethane, chloropentafluoroethane and similar halogenated hydrocarbons. Mixtures of these are also useful. Chemical blowing agents include azodicarbonamide, azobisisobutyronitrile, dinitrosopentamethylenetetramine, paratoluenesulfonylhydrazide, and the like. Mixtures of chemical blowing agents and the aforementioned volatile organic blowing agents are also useful. In addition to the aforementioned compounds and blowing agents, the foamable compositions may also contain small amounts of metal soaps, usually metal soaps such as zinc stearate, finely divided inorganics such as calcium silicate, as lubricants and foam regulators. . Further, depending on the case, an ultraviolet deterioration inhibitor, an antistatic agent, a stabilizer, a coloring agent, a lubricant, etc. may be added in an amount of 5% by weight or less. The method of the invention can be applied to the production of foamed products of any shape, such as sheets, blocks, rods, tubes, as well as wires, cable jackets, molded articles, etc. The evaluation method and evaluation scale used in the present invention are shown below. The effects of the present invention are evaluated based on the shrinkage rate after foaming and the surface condition of the foam after dimensional stabilization. (a) Shrinkage rate after foaming (volume %) Shrinkage rate n days after foaming = (volume of foam after 1-n days/volume of foam immediately after foaming) x 100 Approximately 25m/m,
The diameter is measured using a caliper (JIS 1st class) and the length is measured using a steel ruler (JIS 1st class), based on the volume calculated from the dimensions measured immediately after foam molding. After n days, the diameter and length are similarly measured, the volume is calculated, and the shrinkage rate is determined using the above formula. (b) Surface condition of foam after dimensional stabilization Perform relative evaluation. (Sign) (Evaluation) ◎ Almost no wrinkles and excellent smoothness. 〇 Wrinkles are visible to the naked eye, but are usually acceptable for commercial use. × There are many wrinkles and the product value is poor. From an industrial and practical standpoint, it is preferable for the foam to have less shrinkage, but the initial shrinkage rate (one day after foaming) is required to be approximately 15% or less. Not only does it take a long time (about one month or more), but the surface condition of the foam is also poor. Furthermore, the initial shrinkage rate and 10
It is preferable that the difference from the shrinkage rate after a day is within about 10%; if it is more than that, it is not preferable in terms of dimensional control, and as a result, the variation in the dimensions of the product becomes large. Next, the content of the present invention will be specifically explained using examples. All parts and percentages are by weight unless otherwise specified. Example 1 and Comparative Example 1 Resin: Ethylene-vinyl acetate copolymer (vinyl acetate content 10%, density 0.93 g/cm ³ MI=
1.5, Sumitomo Chemical Evatate D-2021) 100 parts Cell control agent: Calcium stearate 0.1 part Calcium silicate 0.6 part Each composition containing the above resin, cell control agent, and the compound shown in Table 1 was prepared using a round hole with a diameter of 5 m/m. The mixture was melted through a single screw extruder with a diameter of 40 m/m equipped with a die, kneaded with a volatile organic foaming agent separately supplied to the extruder, and extruded and foamed through the die. In Table 1, compounds ABC and D are distearyl malonic acid ester, di(monoethylene glycol stearate) malonic acid ester,
Distearylmalonic acid amide is a malonic acid ester of a polyoxyethylene derivative (n=10) of stearylamide, and the blowing agents are dichlorodifluoromethane, 1,2-dichlorotetrafluoroethane, and butane, respectively. The compositions shown in Table 1 were foamed in the same manner as in Example 1 except that the additives were changed. The results are also listed in Table 1. In all cases, shrinkage occurred after foaming. Even if it is left for a long time, it does not recover to the state immediately after foaming, and the surface of the obtained foam has significant wrinkles and unevenness, and is of poor quality. In Table 1, additives A', B', and C' are didecane malonic acid ester, di(monoethylene glycol capric acid) malonic acid ester, and dicapryl malonic acid amide, respectively. Figures 1 and 2 show changes in the volume and weight of the foam over time. It is clear that when the resin composition of the present invention is foamed, an excellent foam with very little change in volume over time can be obtained. Furthermore, when comparing the weight changes, it is clear that the permeation of the blowing agent gas is suppressed, and the change in volume is small. Therefore, the surface appearance of the foam is excellent. This is thought to be due to preventing or weakening the escape of foaming gas in the foam. Example 2 and Comparative Example 2 In Example 1 and Comparative Example 1, the resin was polyethylene (density 0.919 g/cm ³ , MI = 2.0 Asahi Dow F
-1920) and extrusion foaming was carried out under the same conditions except that 0.06 part of calcium stearate and 0.36 part of calcium silicate were used as foam control agents. The results are shown in Table 2. Example 3 0.3% by weight of dicumyl peroxide as a crosslinking agent and 1.5% by weight of anti-shrinkage agent A were kneaded into the same polyethylene resin used in Example 2 to produce a crosslinked polyethylene resin with a crosslinked gel fraction of 60% ( Expandable crosslinked polyethylene resin particles (diameter: 1.2 mm) were impregnated with dichlorodifluoromethane by pressurizing and heating in a pressure container, and then cooled.

[Table] Hydrofluoromethane (containing 14% by weight) was heated and foamed with steam (heating conditions, steam pressure 0.23Kg/cm ²
G45 seconds). The obtained primary expanded particles were uniform expanded particles with a density of 90 kg/m ³ . Next, the primary foamed particles were placed in a pressure-resistant container and treated at 80°C for 13 hours while being pressurized with air at a pressure of 10 Kg/cm ² to a pressure of 0.32 Kg/cm ^{2 .}
The mixture was foamed through water vapor of G to obtain secondary foamed particles having a density of 25 kg/m ³ . While compressing the secondary foamed particles at an air pressure of 1.5 kg/cm ²
-120 type) mold and heated with steam at a pressure of 1.2 kg/cm ² G to form a molded product. The density of the obtained molded product was 31 Kg/m ³ , excellent fusion between particles and closed cell properties were less than 0.01. Comparative Example 3 Expanded particles were produced in the same manner as in Example 3, except that anti-shrinkage agent A was not added. The density of the obtained primary expanded particles was 110 Kg/m ³ , and the density of the secondary expanded particles was 30 Kg/m ³ . All of these particles have shrunk compared to Example 3, and have many wrinkles on the surface.

【table】

[Table] The particles were small. Also, the life of the expandable particles impregnated with the blowing agent was significantly shorter than in Example 3 (6 hours), being only 20 minutes. Furthermore, the molded foam had larger closed cell characteristics (0.015) than Example 3, and was inferior in terms of cushioning performance and mechanical properties. Example 4 Polystyrene resin (Asahi Dow Styron)
680, MI=8.0) 100 parts by weight of additive A2 of Example 1
A resin composition containing 0.5 parts by weight of talc and 0.5 parts by weight of talc was foamed in the same manner as in Example 1 using 10.0 parts by weight of dichlorodifluoromethane (F-12). The weight of the blowing agent in the obtained foam (foam density: 40 kg/m ³ ) was determined to be 9.5 parts by weight/100 parts by weight of resin. Further, even when the amount of F-12 added was reduced to 8 parts by weight, a foam with a density of 40 kg/m ³ was obtained. Comparative Example 4 A foam was obtained in the same manner as in Example 4 except that Additive A was not added. The weight of the blowing agent in the foam (density 40Kg/m ³ ) is
The amount was 7.4 parts by weight/100 parts by weight of resin. It is clear that the gas efficiency of the blowing agent is improved by adding the compound of the present invention, and foaming can be achieved with a small amount of addition.

[Brief explanation of the drawing]

Figure 1 is a graph showing changes in foam volume over time.
FIG. 2 is a graph showing changes in foam weight over time.

Claims (1)

[Claims] 1. In the thermoplastic synthetic resin, the following general formula [],
A foaming synthetic resin composition containing at least one compound represented by [ ] in an amount of 0.1 to 10% by weight based on the resin. [In the formula, R ₁ is an aliphatic hydrocarbon group having 11 to 24 carbon atoms or an aliphatic carboxylic acid residue, R ₂ is an aliphatic polyhydric alcohol residue having 1 to 5 carbon atoms, _R3 is an aliphatic dicarboxylic acid residue having 2 to 14 carbon atoms, n is a positive integer of 0 to 100, and m is 1 or 2. 2. The composition according to claim 1, wherein the thermoplastic synthetic resin is a polyolefin resin. 3. The composition according to claim 1, wherein the thermoplastic synthetic resin is polyethylene or an ethylene copolymer of ethylene and another copolymerizable monomer.