JP2859983B2 - Extruded propylene resin foam, molded article and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an extruded propylene resin foam, a molded article and a method for producing the same.

[0002]

2. Description of the Related Art As a method for producing a long-sized foam or a sheet-like foam for forming a container or the like, a thermoplastic resin is melt-kneaded with a foaming agent in an extruder, and then subjected to low pressure. An extrusion foaming method of extruding and foaming is widely used.

In the extrusion foaming method of an olefin resin, when a melt-kneaded product of a resin and a foaming agent is extruded under a low pressure from an extruder, foaming is performed by expanding the foaming agent in the melt-kneaded material. However, if the temperature of the resin is increased, the viscosity drops sharply, the resin cannot retain the foaming agent, escapes from the resin and becomes a foam of open cells, and conversely, the resin temperature is increased to increase the viscosity of the resin. When the temperature is lowered, the crystallization of the resin proceeds, and as a result, the foam does not foam sufficiently and uniformly, and the foam surface becomes uneven, so that the extrusion foaming is performed with sufficiently uniform foaming and the foaming agent is mixed into the resin. It is necessary to perform viscoelasticity which can be maintained at a temperature of the resin. The temperature range in which viscoelasticity suitable for foaming is obtained differs depending on the type of resin, and this temperature range is generally referred to as a foaming suitable temperature range.

[0004]

However, the propylene-based resin having a higher degree of crystallinity than low-density polyethylene or the like greatly changes the viscoelasticity of the resin due to a slight temperature change, and has a very narrow temperature range for foaming. It is very difficult to carry out extrusion foaming while maintaining the resin temperature within such a narrow temperature range, and when the extrusion foaming temperature fluctuates and deviates from the appropriate foaming temperature range, the foamed portion has an open-cell structure. And the surface became uneven, and it was difficult to obtain a foam having good overall and uniform properties. Conventionally, in the case of a non-crosslinked propylene-based resin, a relatively good foam can be obtained only at a low expansion ratio having a density exceeding 0.2 g / cm ³ or at a density of 0.013 g / cm ^3. It has a high expansion ratio of less than. The above-mentioned problems are considered to be caused by the high crystallinity of the propylene-based resin, and the density is 0.
Extruded foams having a low expansion ratio of more than 2 g / cm ³ can be obtained relatively favorably because the ratio of the resin is larger than the amount of the foaming agent. It is considered that the reason is that the temperature can be set to a considerably higher temperature. The density is 0.013 g / cm ³
The reason why a foam having a high expansion ratio of less than 1 can be obtained relatively favorably is as follows. Generally, a foaming olefin-based resin in the process of extrusion foaming is subjected to a cooling operation from the outside using a cooling means, thereby solidifying the cell walls to obtain a good foam. However, since the propylene-based resin has a higher degree of crystallinity than low-density polyethylene, the calorific value during crystallization is large. This heat hinders the cooling and thus the solidification of the cell walls, and breaks or deforms the cells of the propylene-based resin in the process of foaming. Therefore, by blending a large amount of a foaming agent and foaming, the temperature of the propylene-based resin in the process of foaming is rapidly lowered by utilizing the heat of vaporization (heat of expansion) of the foaming agent, thereby promoting the solidification of the cell wall. . Further, a large amount of the foaming agent has a function of delaying crystallization of the resin in the extruder. As a result, a relatively good foam can be obtained. However, in this case, the foam obtained necessarily has a high expansion ratio of less than 0.013 g / cm ³ due to the necessity of blending a large amount of the foaming agent. Also, in this case, the suitable foaming temperature range is only 0.6.
It is only about ° C.

In view of the fact that only extruded propylene-based resin foams having a high or low expansion ratio can be obtained, the present invention relates to an extruded propylene-based resin foam having a density of 0.2 to 0.013 g / cm ^3. It is another object of the present invention to provide a method and the like which can be easily manufactured.

[0006]

That is, the extruded propylene resin foam of the present invention is an extruded foam having a non-crosslinked propylene resin as a base material, and the extruded foam of the base resin at 230 ° C. Melt tension is 7gf or more
And the half-crystallization time at the crystallization temperature + 15 ° C. is 8
It is characterized by being at least 00 seconds . The extruded foam of the present invention is a sheet-like foam having a density of 0.6 to 0.018 g / cm ³ and a thickness of 0.1 to 5 mm, or an inorganic filler having a total weight of 15 to 50% by weight in a resin. Density containing 1.2
To 0.1 g / cm < ³ > and 0.1 to ³ mm in thickness. The molded article of the present invention is obtained by heating the above-mentioned extruded sheet-like foam and secondary molding it into a desired shape.

Production of extruded propylene resin foam of the present invention
The manufacturing method is such that the melt tension at 230 ° C. is 7 gf.
The half crystallization time at the crystallization temperature + 15 ° C.
Foaming with a non-crosslinked propylene resin having a viscosity of 800 seconds or more
And melt-kneading the agent in an extruder under high temperature and high pressure, and then extruding the melt-kneaded product through a die attached to the tip of the extruder under a lower pressure than in the extruder to foam.

A non-crosslinked propylene resin having a melt tension at 230 ° C. of 7 gf or more or a melt tension at 230 ° C. of 7 gf used in the present invention.
The non-crosslinked propylene-based resin having a crystallization temperature of + 15 ° C. and a half-crystallization time of 800 seconds or more is a low-temperature decomposition type of a linear propylene-based resin having a total isotactic structure including, for example, low-molecular-weight polypropylene. (Decomposition temperature: room temperature to about 120 ° C.)
It can be obtained by, for example, heating to 0 ° C. or less and re-bonding the low-molecular-weight polypropylene to the linear propylene-based resin as a branched chain. Usually, the linear propylene-based resin is mainly a branch having a long-chain branch at an end portion. It is believed to have a parting structure. Examples of the linear propylene-based resin include a propylene homopolymer and a copolymer of propylene and another olefin. Other olefins copolymerizable with propylene include ethylene, 1-butene, isobutylene, 1-pentene, 3-methyl-1-butene,
-Hexene, 3,4-dimethyl-1-butene, 1-heptene, 3-methyl-1-hexene and the like. Examples of the low-temperature decomposition type peroxide include di (s-butyl) peroxydicarbonate, bis (2-ethoxy) peroxydicarbonate, dicyclohexylperoxydicarbonate, di-n-propylperoxydicarbonate, di-n- Examples thereof include butyl peroxy dicarbonate, diisopropyl peroxy dicarbonate, t-butyl peroxy neodecanoate, t-amyl peroxy neodecanoate, t-butyl peroxy pivalate, and the like. The non-crosslinked propylene resin used in the present invention, the linear propylene resin of the isotactic structure, while stirring in a reactor equipped with a stirrer, replacing the inside of the reaction vessel with an inert gas such as argon, The above peroxide is usually added in an amount of 5 to 50 mmol per 1 kg of the resin, and the mixture is continuously stirred, up to about 120 ° C, preferably 70 to 1
It is obtained by heating to about 05 ° C. to cause a reaction (usually for 30 to 120 minutes), and then terminating the reaction. When terminating the reaction, a reaction terminator such as methyl mercaptan is introduced into the reaction vessel, or the reaction product is added to
For example, a method of heating to about 150 ° C. for about 20 to 40 minutes is employed.

In the present invention, not only the above resin can be used alone, but also other resins can be mixed with the above resin. As the resin used in combination, for example, a propylene-based resin other than the above, or high-density polyethylene, low-density polyethylene, linear low-density polyethylene,
Ethylene resins such as linear ultra-low density polyethylene, ethylene-butene copolymer, ethylene-maleic anhydride copolymer, butene resins, polyvinyl chloride, vinyl chloride such as vinyl chloride-vinyl acetate copolymer Resins, styrene resins and the like.

In the present invention, the melt tension of the resin can be measured by a melt tension tester. In the present invention, a crystallization rate measuring device can be used for measuring the half-crystallization time. To measure the semi-crystallization rate, first, the support holding the film-like sample is
The sample is completely melted by placing it in an air bath of a crystallization rate measuring instrument. Then, the optical path of the light source and the optical sensor is placed in an oil bath in which the molten sample and the support together with the sample are kept at a temperature of 15 ° C. The voltage of the light source is adjusted so that a constant amount of light is always detected by the optical sensor until the melted sample solidifies again, so as to obtain a voltage-time curve as shown in FIG. Assuming that the voltage when the voltage in this curve becomes a constant value is V ₀ , the voltage is Ｖ V ₀
The time required to reach was defined as the half-crystallization time.

The foam of the present invention may be a sheet-like foam or a plate-like thick foam, but in the case of a sheet-like foam,
Those having a density of 0.6 to 0.018 g / cm ³ and a thickness of 0.1 to 5 mm are preferred. In the case of a plate-like foam, the density is 0.18 to 0.1.
It is preferably 018 g / cm ³ and 10 to 100 mm in thickness.

In the foam of the present invention, in the case of a sheet-like foam, the resin preferably contains 15 to 50% by weight of the total weight of the inorganic filler. Examples of the inorganic filler include talc, silica, calcium carbonate, clay, zeolite, alumina, barium sulfate and the like. It is preferable that these particles have an average particle size of 1 to 70 μm. Such a sheet-like foam containing a large amount of an inorganic substance can improve heat resistance and reduce the calorie burned during incineration.

The present invention includes a molded article obtained by heat-molding the above-mentioned foamed sheet. Examples of the method for forming the sheet-like foam include vacuum forming, pressure forming, and applications of these, such as free drawing forming, plug and ridge forming, ridge forming, matched mold forming, straight forming, drape forming, reverse draw forming, and the like. Air slip molding,
Plug-assist molding, plug-assist reverse draw molding, a method combining these, and the like can be applied.

As a method for obtaining the extruded foam of the present invention, there is a method in which a resin and a foaming agent are melt-kneaded in an extruder, and the melt-kneaded material is extruded under a low pressure through a die attached to a tip of the extruder to foam. Adopted. In particular, in order to obtain a sheet-like foam, a circular die having an annular lip is used, a foam is extruded from the lip of the die to obtain a tube-like foam, and then the tube is cut open to form a sheet. Is usually adopted. In order to obtain a thick extruded foam, a large extruder may be used. However, a small extruder is used to melt the resin and the foaming agent in the small extruder 1 as shown in FIG. After kneading, the melt-kneaded material in the extruder 1 is extruded and stored in an accumulator 2 which has a larger discharge capacity than the extruder 1 and is maintained at a pressure at which foaming does not occur in the melt-kneaded material. It is preferable to employ a method in which the foam is extruded under a low pressure through a die 3 attached to the tip of the accumulator 2, foamed, and pressed by a molding device 4 to obtain a plate-shaped foam having a predetermined thickness. still,
In FIG. 2, 5 is a hopper for supplying raw material resin, 6 is a foaming agent supply pipe, 7 is a piston, 8 is a piston rod, and 9 is a cylinder.

As the foaming agent, an inorganic foaming agent, a volatile foaming agent, a decomposition-type foaming agent and the like can be used. As the inorganic foaming agent, carbon dioxide, air, nitrogen and the like can be used. The volatile blowing agents include propane, n-butane, i
-Butane, pentane, aliphatic hydrocarbons such as hexane, cyclobutane, cycloaliphatic hydrocarbons such as cyclopentane,
Halogenated hydrocarbons such as trichlorofluoromethane, dichlorodifluoromethane, dichlorotetrafluoroethane, methyl chloride, ethyl chloride, and methylene chloride can be used. Further, as the decomposition type foaming agent, azodicarbonamide, dinitrosopentamethylenetetramine, azobisisobutyronitrile, sodium bicarbonate and the like can be used. These foaming agents can be used by being appropriately mixed. The amount of the foaming agent used depends on the type of the foaming agent, the desired expansion ratio, and the like. For example, the standard of the amount of the foaming agent used to obtain a foam having a density of about 0.2 to 0.013 g / cm ³ is as follows. And about 0.5 to 25 parts by weight (in terms of butane) of a volatile foaming agent per 100 parts by weight of the resin. The amount of the foaming agent used to obtain a foam having a density of more than 0.09 g / cm ³ is estimated based on 100 parts by weight of the resin.
In the case of an inorganic foaming agent, it is about 0.1 to 10 parts by weight, and in the case of a decomposition type foaming agent, it is about 0.1 to 5 parts by weight.

In the present invention, a foam regulator may be further added to the melt-kneaded product of the resin and the foaming agent. Examples of the cell regulator include inorganic powders such as talc and silica, acidic salts of polycarboxylic acids, and reaction mixtures of polycarboxylic acids with sodium carbonate or sodium bicarbonate. It is preferable to add about 13 parts by weight or less of the foam control agent per 100 parts by weight of the resin (except when the inorganic filler is contained in a large amount in the resin). Further, if necessary, additives such as a heat stabilizer, an ultraviolet absorber, an antioxidant, and a colorant can be added.

[0017]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples. Table 1 shows the physical properties of the resins used in Examples and Comparative Examples. In Examples and Comparative Examples, the amounts of the foaming agent and the foam control agent were such that the sum of these and the resin was 1
It is a weight ratio when it is set to 00 parts by weight. The melt tension of the resin used was measured using a melt tension tester type II manufactured by Toyo Seiki Seisaku-sho, Ltd. The crystallization time measuring device MK- manufactured by Kotaki Shoji Co., Ltd. was used to measure the half-crystallization time.
Type 801 was used. The measurement of the melt tension is performed as follows. A molten propylene resin heated to 230 ° C. from a melt indexer nozzle (diameter 2.095 mm, length 8 mm) was loaded from above with a load of 10 mm /
Extruded into a string at a constant speed for a minute, the extrudate is passed through a tension detection pulley, guided to a feed roll and wound, while the winding speed is gradually increased to cut the string,
The tension immediately before the cutting is read, and this is defined as the melt tension (gf). However, if the string-like material is not cut at a winding speed of 78.5 m / min, the tension at this time is read and this is defined as the melt tension.

Examples 1 to 6 and Comparative Examples 1 to 3 Resins, isobutane and talc were mixed in the proportions shown in Table 2 by 50
Extruder with a single screw of mmφ (L / D ratio = 4
6), melt-kneaded, extruded and foamed through a circular die attached to the tip of the extruder and having a lip with a diameter of 75 mm and a gap of 0.3 mm to obtain a tubular foam, and then cut and open this tube to foam I got a sheet. Table 2 shows the extrusion foaming temperature, the expansion ratio of the foam sheet, and the state of the sheet. The extrusion foaming temperature was measured at a breaker plate portion provided with a breaker plate provided with a mesh screen for removing foreign substances and the like in the resin, between the extruder and the circular die. The state of the foamed sheet is as follows: ・ ・ ・: The surface irregularities are small , there are substantially no open cells, and the whole has substantially uniform properties. X: The surface is very uneven or corrugated, or has many portions with an open cell structure, and the whole does not have uniform properties. Was evaluated.

[0019]

[Table 1]

[0020]

[Table 2]

Example 7 2 parts by weight of isobutane and 5 parts by weight of talc were melt-kneaded in the same extruder as in the above-mentioned example with respect to 93 parts by weight of resin A, and then a circular cylinder having a diameter of 75 mm and a gap of 0.5 mm was obtained. It was extruded from a die to obtain a tubular foam. Rings for air blowing are installed inside and outside of this tubular foam to blow air to the outer and inner surfaces of the tube, and the inner surface of the tubular foam is cooled with a cooling mandrel (mandrel diameter is lip (2.0 times the diameter) to obtain a tube having a blow ratio of 2.0 times. The tube was cut open to obtain a sheet. Extrusion foaming temperature is 162
C., 165.degree. C., and 168.degree. C., and the state of the sheet obtained at each extrusion foaming temperature is shown in Table 3. The evaluation of the state of the foamed sheet was in accordance with the above example.

[0022]

[Table 3]

Comparative Example 4 2 parts by weight of isobutane per 96.5 parts by weight of resin E,
1.5 parts by weight of talc were melt-kneaded in the same extruder as used in Example 5, and then extruded from the same circular die to foam. When the extrusion foaming temperature exceeds 181 ° C., the foaming agent gas escapes from the resin and a foam cannot be obtained. When the extrusion foaming temperature is 181 ° C., a foam having a closed cell structure can be obtained. When a tubular foam was passed through a mandrel, the tube was torn and a good sheet could not be obtained. When the extrusion foaming temperature was 179 ° C., the tube did not tear even when the tube-shaped foam was passed through the mandrel, but the tube slipped on the mandrel and became difficult to take off. In addition, the extrusion foaming temperature is set to 1
When the temperature was lowered to 78 ° C., the pressure of the extruder increased, and extrusion foaming was impossible. The suitable foaming temperature range was as narrow as about 180 ± 1 ° C. The foamed sheet obtained when the extrusion foaming temperature was 179 ° C. had a thickness of 0.9 mm and a foam density of 0.27 g /
cm ³ , but the surface unevenness was severe, the surface was partially torn, and the whole was not a homogeneous foam sheet.

Examples 8-10 Resin B, butane and monosodium citrate were prepared in Table 4
Tandem extruder (first extruder: screw diameter 65 mm, L / D = 34, second extruder: screw diameter 9)
0 mm, L / D = 32), melt-kneaded, and extruded into a tube from a circular die with a gap of 0.5 mm and a diameter of 65 mm attached to the tip of the extruder, while air is applied to the inner and outer surfaces of the foam. , And the inner surface was further taken off so as to be in contact with a cooling mandrel (mandrel diameter 200 mm). Thereafter, the tubular foam was cut out from one end in the extrusion direction to form a sheet. The extrusion conditions at this time and the properties of the obtained foamed sheet are also shown in Table 4.

[0025]

[Table 4]

Next, each of the sheets obtained in Examples 8 to 10 was heated in an oven at an atmosphere temperature of 165 ° C. for 14 hours.
After heating for 11 seconds and 10 seconds and performing plug-assist vacuum forming, a container having a high degree of homogeneity without pear or breakage was obtained. This container is a dish-shaped container having storage portions 11 and 12 on both sides of the partition 10 as shown in FIGS. 3 and 4, and in FIGS. 5
cm, b: 11.2 cm, c: 6.3 cm, d: 11 cm, e: 9c
m, f: 4 cm, g: 3.5 cm, h: 2.5 cm.

Comparative Example 5 After 96.5 parts by weight of resin E, 2 parts by weight of butane and 1.5 parts by weight of talc were melt-kneaded in the same extruder as used in Example 9, and then the same circular die was used. Extruded and foamed. When the extrusion foaming temperature exceeded 173 ° C., the foaming agent gas escaped from the resin, and a foam was not obtained.
When the extrusion foaming temperature is 172 ° C., a foam having a closed cell structure can be obtained. However, when the tubular foam obtained by extrusion foaming is passed through a mandrel, the tube is torn, and the tube slips on the mandrel. Was difficult. Further, when the extrusion foaming temperature was lowered to 170 ° C., the pressure of the extruder was increased, and extrusion foaming was impossible. The foamed sheet obtained when the extrusion foaming temperature was 172 ° C had a thickness of 0.6 mm and a density of 0.5.
Although it was 6 g / cm ³ , the surface unevenness was severe , the surface was partially torn , and the whole was not a uniform foam sheet.

Examples 11 to 13 and Comparative Examples 6 to 8 An extruder (L / D ratio = 48) equipped with a single screw having a diameter of 45 mmφ has an accumulator of 90 mmφ, a volume of 5 liters, and a discharge rate of 1980 kg / hour. Mounting, Table 5
Is melt-kneaded in an extruder, the melt-kneaded material is extruded into an accumulator maintained at a temperature of 160 ° C. and a pressure of 40 kg / cm ² and temporarily stored in the accumulator, and then melt-kneaded. The product was extruded from a die with a lip gap of 1.5 mm attached to the tip of the accumulator to obtain a plate-like foam. The state of the obtained foam is shown in Table 5. The properties of the plate-like foam are as follows: ○ ・ ・ ・ Small surface irregularities, virtually no open cell portion, and a substantially uniform foam as a whole × ・ ・ ・ Surface irregularities and corrugation are severe, and The foam was evaluated as a foam having many portions and not entirely homogeneous. After production, the foams obtained in Examples 11 to 13 were left at room temperature for one week, and the density was measured. On the other hand, in the case of Comparative Examples 6 to 8 , the foam contracted significantly during the production.

[0029]

[Table 5]

Example 14 2.9 parts of isopentane per 64.7 parts by weight of resin A
After melt-kneading 32.4 parts by weight of talc and 32.4 parts by weight in the same extruder as in Examples 1 to 6, the mixture was extruded through a circular die having a diameter of 75 mm and a gap of 0.5 mm (foaming temperature: 165 ° C.).
A tubular foam was obtained. Rings for air blowing are installed inside and outside of this tubular foam to blow air to the outer and inner surfaces of the tube, and the inner surface of the tubular foam is further cooled with a cooling mandrel (the mandrel diameter is the lip diameter). (2.0 times), and a tube having a blow ratio of 2.0 times was obtained. The tube was cut open to obtain a sheet. The obtained sheet has a thickness of 0.67 mm and a density of 0.67 mm.
0.48 g / cm ³ with small surface irregularities and virtually independent
It was air bubbles and had substantially uniform properties throughout. Next, this sheet was heated in a heating furnace at an atmosphere temperature of 165 ° C. for 13 seconds, and plug-assisted vacuum forming was performed. As a result, a dish-like container having no pear or breakage and having a shape faithful to the mold was obtained. The shape of this container is similar to that shown in FIGS. In addition, when the calorie burned of this container was measured, it was 7500 cal / g, and 11300 cal / g of a container made of the same resin in which talc was not mixed at all.
The calorie burned was significantly lower than g.

[0031]

As described above, in the method of the present invention, since the foaming suitable temperature range is wider than in the conventional extrusion foaming method using a non-crosslinked propylene resin as a base material, it is easy to control the extrusion foaming temperature. By using a non-crosslinked propylene-based resin as a base resin, a propylene-based resin extruded foam having a uniform and excellent properties can be obtained. The method of the present invention can be applied to a case where a sheet-like foam is produced or a case where a thick plate-like extruded foam is produced to obtain a good foam. The extruded foam obtained by (1) has extremely small shrinkage and corrugation, and even when a container or the like is formed using the sheet-like foam, the obtained molded article has good properties without shrinkage or the like.

[Brief description of the drawings]

FIG. 1 is a voltage-time curve obtained by crystallization rate measurement.

FIG. 2 is a schematic view showing an example of an extrusion foaming apparatus.

FIG. 3 is a plan view of a dish-shaped container obtained by molding the sheets obtained in Examples 8 to 10.

FIG. 4 is a side view of a dish-shaped container obtained by molding the sheets obtained in Examples 8 to 10.

[Explanation of symbols]

 Reference Signs List 1 extruder 2 accumulator 3 die

Continuation of the front page (51) Int.Cl. ⁶ Identification code FIB29L 7:00 C08L 23:10 (56) References JP-A-57-197132 (JP, A) JP-A-2-298536 (JP, A) Antec 90 (May 7-11), 717-720, M.P. B. Pradley, E. M. Philips "New foamable polypropylene polymers", [ANTEC 90 (May 7-11), Conference Proceedings MB. Bradley and E.A. M. Philips; "Novel Foamable Polypropylene Polymers"] (58) Fields investigated (Int. Cl. ⁶ , DB name) B29C 47/00-47/96 C08J 9/00-9/42

Claims (5)

(57) [Claims] The method according to claim 1] non-crosslinked propylene resin A extruded foam as a base, with a melt tension at 230 ° C. of the propylene-based resin as a base resin is more than 7 gf,
And a half-crystallization time of 800 at a crystallization temperature of + 15 ° C.
A propylene-based resin extruded foam characterized in that the time is not less than seconds . 2. The extruded propylene resin foam according to claim 1, which is a sheet foam having a density of 0.6 to 0.018 g / cm ³ and a thickness of 0.1 to 5 mm. 3. A resin having a density of 1.2 to 0.1 g / cm ³ , containing 15 to 50% by weight of a total weight of an inorganic filler in a resin;
2. The extruded propylene-based resin foam according to claim 1, which is a sheet-like foam having a thickness of 0.1 to 3 mm. 4. A molded article of a propylene-based resin extruded foam obtained by heating and molding the sheet-shaped foam according to claim 2 or 3 . 5. A melt tension at 230 ° C. of 7
Semi-crystallization at gf or more and crystallization temperature + 15 ° C
The time and non-crosslinked propylene resin which is 800 seconds or more and a foaming agent, and melt-kneaded under high temperature and high pressure in an extruder, followed by low pressure from the extruder through a die attached to the melt-kneaded material in the extruder tip A method for producing a foamed extruded propylene-based resin, characterized by extruding into a foam.