JPH0373579B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a highly foamable polyolefin composition, and more particularly to a highly foamable polyolefin composition comprising a polyolefin, a volatile organic blowing agent, a specific amide, and a specific amine. Until now, it has been known to obtain a polyolefin foam molded product by adding a volatile organic foaming agent to non-crosslinked polyolefin and foaming it by extrusion. It is widely used as materials, packaging materials, etc. However, in general, polyolefins have low viscoelasticity when heated and melted and cannot sufficiently maintain the gas pressure of the blowing agent, so they collapse when the formed cells grow to a certain extent, and generate heat when cooled and crystallized. , the cells do not cool and solidify smoothly, and because the foaming agent is highly permeable to gas, it easily evaporates when the foaming agent evaporates, preventing sufficient foaming. , it is difficult to obtain a highly foamed product with good appearance. For example, in the method proposed so far (Japanese Patent Publication No. 35-4341), the foaming conditions that allow for high foaming are limited to a very narrow range, and the foaming conditions are not maintained for a long time. Since it is difficult to control and requires special equipment, it cannot necessarily be said to be a satisfactory method for industrial implementation. To solve these problems, in order to make polyolefin into a highly foamed molded product with an expansion ratio of about 5 times or more, polyolefin is first treated with peroxide or radiation to crosslink it, and then this is foam-molded. However, this method requires a special process for crosslinking.
It is inevitable that products will cost more. On the other hand, polyethylene with a high degree of crystallinity, such as high-density polyethylene, has a large change in viscoelastic properties near its melting point compared to low-density polyethylene, so the extrusion temperature range is significantly restricted. Maintaining proper conditions and controls for continuous extrusion molding for body purposes becomes increasingly difficult. In addition, because high-density polyethylene has a higher degree of crystallinity than low-density polyethylene, it generates a large amount of heat during the crystallization described above, and as a result, the solidification of cells during cooling is further hindered, resulting in cell destruction and deformation. This results in decreased extrusion moldability and product quality deterioration. In general, the thicker the foam, the more heat is accumulated during crystallization, and the cells no longer cool and solidify smoothly, so this tendency becomes more pronounced. Furthermore, while low-density polyethylene has long chain branches and high melt viscoelasticity, high-density polyethylene does not have long chain branches and has low melt viscoelasticity, so it is extruded from a die together with a blowing agent.
During foam molding, the die did not have sufficient pressure resistance to suppress the generation of bubbles, and the cells already formed in the die were destroyed by heat and shear force during the extrusion foaming process. This results in deterioration of the quality of the foam. This tends to increase as the cross-sectional area of the die opening increases, that is, as the thickness of the foam increases. To solve this problem, it is possible to increase the resin pressure by increasing the extrusion rate. Extremely special equipment with a large capacity must be used, and if the extrusion rate is excessively increased, flow disturbances such as melt fractures will occur, resulting in a decrease in extrusion moldability, which is impractical. In this way, all of the methods known so far for producing high-quality, highly foamed molded products using polyethylene as a raw material are not necessarily satisfactory as industrially viable methods. However, it has been difficult to obtain a thick foam with a particularly large cross-sectional area. In view of these circumstances, the present inventors aimed to obtain a highly foamed molded product having a good appearance, an independent cell structure, and a large cross-sectional area using non-crosslinked polyethylene, especially high-density polyethylene, as a raw material. As a result of extensive research, by using a combination of a specific amide and a specific amine as a foaming modifier,
The inventors have discovered that the object can be achieved, and have completed the present invention based on this knowledge. That is, the present invention comprises (a) polyolefin and (b)
Volatile organic blowing agent and (c) general formula (R ₁ in the formula is a hydrocarbon group having 1 to 23 carbon atoms) and at least one amide represented by the general formula (H-) _X N-[-(R ₂ -O-) _y H] _{3 -X} ...() (R ₂ in the formula is an alkylene group having 1 to 5 carbon atoms, y
is an integer of 1 to 10, and x is an integer of 0 or 1 to 2. It is. In the composition of the present invention, as a foaming modifier,
As the component (iii), it is necessary to use a foaming improver that is a combination of an amide represented by the general formula () and an amine represented by the general formula (). By using these combinations, it is possible to obtain highly foamable compositions that are more suitable for molding thick-walled foams. The compounds represented by the above general formulas () and () are all known compounds or can be easily produced by known methods.
Examples of amides represented by general formula () include hexane amide, octane amide, decane amide,
Examples include dodecanamide, tetradecanamide, octadecaneamide, and the like. These amides may be used alone or in combination of two or more. Further, as the amine represented by the general formula (), for example, 2-hydroxyethylamine, di-2-
-Hydroxyethylamine, tri-2-hydroxyethylamine, 2-hydroxypropylamine, di-2-hydroxypropylamine, tri-
Mention may be made of 2-hydroxypropylamine, 3-hydroxypropylamine, di-3-hydroxypropylamine, tri-3-hydroxypropylamine, and tri-polyoxyethylamine. These amines exhibit similar effects even if their terminal hydroxyl groups are acylated. Examples of such acylated products include tri-2-hydroxyethylamine monostearate and tri-2-hydroxyethylamine monostearate.
2-hydroxyethylamine distearate, tri-2-hydroxyethylamine tristearate, tri-2-hydroxyethylamine monolaurylate, tri-2-hydroxyethylamine dilaurylate, tri-2-hydroxyethylamine trilaurylate, etc. be able to.
Particularly preferred among these amines are 2-
Hydroxyethylamine, di-2-hydroxyethylamine, tri-2-hydroxyethylamine, di-2-hydroxypropylamine, tri-
2-hydroxypropylamine and the like. These may be used alone or in combination of two or more. The amount of the foaming improver consisting of the amide represented by the general formula () and the amine represented by the general formula () is 0.05 to 15 parts by weight in total per 100 parts by weight of the polyolefin of component (A); It is preferably selected within the range of 0.1 to 10 parts by weight. If this amount is less than 0.05 parts by weight, the effect of increasing the cross-sectional area of the foam will not be sufficient, and if it exceeds 15 parts by weight, the effect will not increase commensurately even if the amount is increased, making it uneconomical. Further, the blending ratio of the amide to the amine is preferably in the range of 80:20 to 1:99 on a weight basis, and particularly preferably in the range of 70:30 to 10:90. If this blending ratio deviates from the above range, the effect of using the two in combination will not be sufficiently exerted. Examples of the polyolefin of component (a) used in the composition of the present invention include polyethylene, polypropylene, polybutene-1, 1,2-polybutadiene, 1,3-polybutadiene, ethylene-propylene copolymer, ethylene or propylene, and others. α of
- Copolymers with olefins, or ethylene-vinyl acetate copolymers, ethylene-ethyl acrylate copolymers, ethylene-vinyl chloride copolymers, ethylene ionomers (zinc or sodium salts of ethylene-acrylic acid copolymers) metal salts of copolymers of ethylene and unsaturated carboxylic acids, such as
Among these, high-density polyethylene with a density of 0.930 g/cm ³ or more is preferred. In the composition of the present invention, these polyolefins may be used alone or in a mixture of two or more, and further, these polyolefins may be used as a main component and other resins may be appropriately mixed. You can also do that. Volatile organic blowing agents as component (b) used in the composition of the present invention include, for example, hydrocarbons and halogenated hydrocarbons, and specific examples of these hydrocarbons include propane, butane, pentane, pentene, hexane, etc. , Specific examples of halogenated hydrocarbons include methyl chloride, dichloride methane, trichloromonofluoroethane, dichlorodifluoromethane, monochlorotrifluoromethane, dichloromonofluoromethane, monochlorodifluoromethane, trichlorotrifluoroethane, dichlorotetrafluoroethane, Examples include monochloropentafluoroethane. Among these, preferred are halogenated hydrocarbons containing at least dichlorotetrafluoroethane, and particularly preferred are halogenated hydrocarbons containing 30% by weight or more of dichlorodifluoroethane. The mixing ratio of the volatile organic blowing agent in the composition of the present invention is 5 parts by weight per 100 parts by weight of polyolefin.
The range is preferably 150 parts by weight, more preferably 10 to 100 parts by weight; if this amount is less than 5 parts by weight, it is difficult to obtain a highly foamed product;
Moreover, if it exceeds 150 parts by weight, the effect of increasing the cross-sectional area of the foam will be reduced. Particularly suitable compositions of the present invention include temperature
The melt index (HMI) measured at 190℃ and a load of 21.6 kg is 35 g/10 minutes or less, and the density is
For high density polyethylene of 0.930g/cm3 or ^more ,
Dichlorotetrafluoroethane as volatile organic blowing agent and other halogenated hydrocarbons such as trichloromonofluoromethane, dichloromonofluoromethane, dichlorodifluoromethane, trichlorotrifluoroethane, methyl chloride, dichloridemethane It is a combination of at least one type of amide and an amide of the general formula () and an amine of the general formula (). The composition of the present invention may contain a commonly used cell nucleating agent, if necessary. Examples of the bubble nucleating agent include inorganic fine powder such as talc and silicon oxide, zinc stearate,
Fine organic powders such as calcium stearate and fine powders that can generate gas when heated such as citric acid and sodium hydrogen carbonate are used. In addition, ultraviolet absorbers, antioxidants, antistatic agents,
Coloring agents and the like can also be included as desired. To prepare the composition of the present invention, predetermined amounts of the components (a) to (d) and optionally added components are added by any method commonly used for preparing a homogeneous mixture. Stir to mix. Particularly suitable are the masterbatch method and the dry blend method. Although there is no particular restriction on the order in which each component is added, the usual method is to mix the components other than the volatile organic blowing agent in advance and then mix this blowing agent in the extrusion foaming step. As a method for producing a foam from the composition of the present invention, for example, a method is usually used in which the composition is prepared under high temperature and high pressure, and then exposed to a low temperature and low pressure region to form a foam. As a molding method at this time, for example, an extrusion foaming method, a press foaming method, an injection foaming method, an in-mold foaming method, etc. can be applied, but the extrusion foaming method is advantageous. In this way, extruded foam molded products of various shapes,
For example, sheets, boards, rods, tubes, pipes,
It is possible to manufacture nets, etc. The composition of the invention is particularly suitable for producing thick boards. The foam obtained from the composition of the present invention is a high foam with an expansion ratio of 5 to 150 times, and has excellent heat insulation and cushioning properties, and can be used as a heat insulating material, a cushioning material,
It is useful as a packaging material, etc. Next, the present invention will be explained in more detail with reference to Examples. The foams in Examples and Comparative Examples were evaluated in accordance with the following evaluation method and criteria. (1) Foaming ratio Foam density after foaming based on JIS-K6767
It was calculated from the weight and volume of the foam after 15 days, and the foaming ratio was determined according to the following formula. Expansion ratio = Resin density before foaming / Density of foam (2) Cross-sectional area coefficient A scale for evaluating suitability for molding thick molded products with a large cross-sectional area, and was determined according to the following formula. Cross-sectional area coefficient=
Foam cross-sectional area/(die opening cross-sectional area) x (foaming ratio) ^2/
3The larger this value is, for example, a circular die will foam more in the diameter direction than in the extrusion direction, and a rectangular die will foam more in the thickness direction than in the extrusion direction. This means that it is suitable for molding thick objects. Additionally, Table 1 shows the additives used in the Examples and Comparative Examples.

[Table] Example 1 High-density polyethylene (density 0.960 g/cm ³ ,
HMI26g/10min, Santec manufactured by Asahi Kasei Industries, Ltd.
To 100 parts by weight of B870), add the prescribed amount of additives shown in Table 2 and 0.1 part by weight of talc as a bubble nucleating agent, dry blend with a Henschel mixer, and then mix thoroughly and uniformly with a kneading extruder. A base material for foam molding was prepared. The first extruder (caliber 30 mmφ, L/D = 30) has a blowing agent inlet in the cylinder, and the second extruder (caliber 40 mm) has a cooling oil jacket in the cylinder.
mmφ, L/D=30) connected in series, the base material was fed to the first extruder heated to a maximum of 220°C at a feeding rate of 4 kg/hour. A foaming composition was prepared by injecting a prescribed foaming agent into the melt-kneaded zone. The blowing agent used was a mixture of dichlorotetrafluoroethane and trichlorotrifluoroethane in an equimolar ratio, and was continuously supplied using a high-pressure pump at a ratio of 50 parts by weight to 100 parts by weight of high-density polyethylene. The composition obtained in this way is supplied to the second extruder through a connecting pipe, where it is gradually cooled to the optimum foaming temperature, and the composition is passed through a rod die with a diameter of 3 mmφ attached to the tip of the second extruder. more extruded,
A foam was obtained. The evaluation results of the obtained foams are shown in Table 2. As is clear from this table, the foams obtained from the compositions of experiment numbers 1 to 3 all exhibit high cross-sectional area coefficients, which indicates that these compositions are suitable for molding thick materials with large cross-sectional areas. All of the foams were foamed to a high magnification, had good appearance and closed cell properties, and had sufficient commercial value. Comparative Example 1 Although the additive was outside the scope of the present invention, a foam was produced in the same manner as in Example 1, except that no additive was used at all. The evaluation results of the obtained foams are shown in Table 2. As is clear from this table, when additives outside the scope of the present invention were used, the foams in Experiments Nos. 4 and 5 were foamed to a high ratio, but the closed cell properties were poor and the cross-sectional area coefficient was small. In Experiment Nos. 6 and 7, the foams were foamed at a high magnification and had excellent appearance and closed-cell properties, but the cross-sectional area coefficient was smaller than in Experiment 1, and the moldability was poor. It was wet. Furthermore, in experiment number 8 in which no additive was used, similar results to those of experiment numbers 4 and 5 were obtained.

[Table] Example 2 A foam was produced in the same manner as in Example 1, except that the types and amounts of additives in Example 1 were changed to those shown in Table 3. The evaluation results of the obtained foam are shown in Table 3. As is clear from this table, in Experiment Nos. 9 to 12, all evaluation items were excellent, and the compositions were suitable for molding thick-walled products. In addition, in Experiment No. 13 in which the total amount of additives was 0.04 parts by weight, although foaming was achieved at a high ratio, the wall thickness formability was slightly inferior to that of Experiments Nos. 9 to 12. In Experiment No. 14, in which the total amount was 20 parts by weight, there was no significant effect on thick-wall formability considering the amount added.

[Table] Example 3 100 parts by weight of high-density polyethylene (Santec B870 manufactured by Asahi Kasei Corporation), 50 parts by weight of an equimolar mixture of dichlorotetrafluoroethane and trichlorotrifluoroethane as a blowing agent, and talc as a bubble nucleating agent. A foam was produced in the same manner as in Example 1 by adding 0.1 part by weight and 2.0 parts by weight of a foaming improver. The foaming improver used in this case was a mixture of diethanolamine and Amide T in various proportions. The relationship between the amount of Amide T used (parts by weight per 100 parts by weight of resin) and the cross-sectional area coefficient for the foam thus obtained is shown in the attached drawing as a graph. As is clear from this figure, when the blending ratio of Amide T and diethanolamine was in the range of 80:20 to 1:99, the effect of increasing the cross-sectional area coefficient was observed due to the combination thereof. Example 4 Polyolefin and blowing agent were tested in Table 4, Experiment No. 15.
~17, with amide as an additive
A foam was produced in the same manner as in Example 1, except that 1.0 part by weight of T and 1.0 part by weight of diethanolamine were used. The evaluation results of the obtained foams are shown in Table 4, Experiment Nos. 15 to 17. As is clear from this table, in Experiment Nos. 15 to 17, all evaluation items were excellent, and the composition was suitable for molding thick molded products. Comparative Example 2 Polyolefin and blowing agent were tested in Table 4, Experiment No. 18.
A foam was produced in the same manner as in Example 1, except that the foam was as shown in Example 1 to 20 and no additives were used. The evaluation results of the obtained foam are shown in Table 4 by experiment number.
Shown in 18-20. As is clear from this table, in Experiment Nos. 18 to 20, the cross-sectional area coefficient was smaller than in Experiment Nos. 15 to 17, and the thickness formability was inferior.

【table】

[Table] Example 5 A foam was produced in the same manner as in Example 1 except that 2 parts by weight of a mixture of equal amounts of di-2-hydroxyethylamine monostearate and Amide T was used as a foaming modifier. This product had a foaming ratio of 53 and a cross-sectional area coefficient of 5.5.

[Brief explanation of drawings]

The drawing is a graph showing the relationship between the composition of the foaming improver and the cross-sectional area coefficient of the obtained foam in the present invention.

Claims (1)

[Claims] 1 (a) polyolefin, (b) volatile organic blowing agent, and (c) general formula (R ₁ in the formula is a hydrocarbon group having 1 to 23 carbon atoms) and at least one amide represented by the general formula (H-) _X N-[-(R ₂ -O-) _y H] _{3 -X} ...() (R ₂ in the formula is an alkylene group having 1 to 5 carbon atoms, y
is an integer of 1 to 10, and x is an integer of 0 or 1 to 2. 2. The composition according to claim 1, wherein the foaming improver is added in a total amount of 0.05 to 15 parts by weight per 100 parts by weight of the polyolefin. 3. The composition according to claim 1 or 2, wherein the polyolefin is a high-density polyolefin. 4. The composition according to claim 1, 2 or 3, wherein the volatile organic blowing agent is a halogenated hydrocarbon including dichlorotetrafluoroethane.