JP2002003637A - Polyolefin-based in-mold foam molded article and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyolefin resin having excellent physical properties such as recoverability, compressive strength and the like and improved appearance quality by reusing regenerated granulated particles of a used polyolefin resin foam. To provide an in-mold foam molded article. SOLUTION: In a polyolefin resin in-mold molded article containing particles obtained by pulverizing an in-mold molded article of polyolefin-based resin expanded particles, the fusion ratio between expanded particles is 80%.
A polyolefin-based resin-molded in-mold molded product characterized by having a recovery rate of at least 75%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cushioning material for transporting electronic parts such as a personal computer and its peripheral devices such as a storage device and a printer, or a semi-finished product thereof (hereinafter simply referred to as a cushioning material). The present invention relates to a polyolefin-based resin-molded in-mold foamed product widely used as (1). More specifically, a polyolefin-based resin molded foam molded article using re-granulated foam particles obtained by crushing a buffer material that has been disposed of at the time of unpacking after transportation,
And its manufacturing method.

[0002]

2. Description of the Related Art In recent years, measures have been taken to convert spent buffer materials made of foam into oil by thermal decomposition or incinerating them. However, these methods are extremely inefficient in energy efficiency or dioxin. There is a problem that harmful substances such as the above are generated and environmental destruction is caused. Therefore, a technique has been developed for regenerating a used cushioning material made of a foam without thermal decomposition or incineration. For example, first, the used buffer material made of foam is once melted by a volume reducer and regenerated into pellets, then mixed with an unused resin pellet in an appropriate amount and formed into resin particles by an extruder, and then a foaming agent is added thereto. Impregnation, heating and foaming to form pre-expanded particles, followed by bead foaming in a conventional manner to obtain an in-mold foam molded article. However, in this regenerating technology, the resin itself deteriorates due to repeated thermal histories before being made into pre-expanded particles, and the mechanical strength such as compression characteristics and tensile characteristics of the obtained in-mold expanded molded article is reduced, The buffering performance that must be provided as a buffer material cannot be satisfied, and the foam structure of the pre-expanded particles also becomes non-uniform. There is a fatal problem that only an in-mold foam molded article having low adhesion strength and appearance quality can be obtained. Furthermore, in this recycling technique, only a non-crosslinked type polyolefin resin in-mold foam molded article can be used, and in the case of a cross-linked in-mold foam molded article, there is a problem of an excessive increase in melt viscosity due to crosslinking. Available and unusable. For the reasons described above, at present, this reproduction technique has not yet been established as a mass production technique.

On the other hand, there is a technique in which a used buffer material made of a foam is pulverized by a pulverizer, and the pulverized pieces are used alone or mixed with unused pre-expanded particles to be re-formed into an in-mold foam molded article. For example, I) Japanese Patent No. 2784528, II)
This is a technique disclosed in Japanese Patent Application Laid-Open No. 10-329222. Specifically, I) is a pulverized piece having a minor axis length of 2 to 7 mm after pulverizing the used Styrofoam type molded article and classifying and removing the finely pulverized piece, and having an average particle size of the maximum of the pulverized piece. It introduces a technique of mixing unused styrofoam pre-expanded particles having a length of less than 1/2 of the minor axis length and molding the resulting mixture in a mold to form an in-mold foam molded article. II) 1-5 mm diameter crushed particles of a foamed molded article in a used mold made of expanded polyethylene, expanded polypropylene, expanded polystyrene, etc., are filled into the molding die by pressure feeding, and then steam is introduced into the molding die to form a mold. It is intended to propose a method for obtaining a molded body.

However, according to experiments performed by the present inventors,
The polyolefin-based resin-molded foam obtained by the method described in the above I) or II) has not only the appearance quality but also the buffering performance of a level which can be practically used as a buffering material. That is, the former technique can be applied when the re-granulated expanded particles are of a styrene type, but cannot be used for a polyolefin type. The reason is that a conventional blowing agent such as an aliphatic hydrocarbon having 4 to 5 carbon atoms or a CFC-based blowing agent has a very high permeation rate with respect to a polyolefin-based material. Since no foaming agent remains, foaming and swelling properties cannot be expected of the foaming agent itself. Therefore, it is mixed with unused pre-expanded particles (the foaming agent does not remain for the same reason). Even when foaming is performed, the voids between the foamed particles are not filled, and only a compact having a remarkable shrinkage phenomenon and water content can be obtained.

[0005] On the other hand, the latter technique, according to the description of II), is a remolded article having a good appearance and quality comparable to that of a new molded article using virgin pre-expanded particles even if the pulverized particles are used alone. However, according to a follow-up test conducted by the present inventor, a serious defect was observed in that voids existed between the particles and the fusion strength between the particles was low.
In order to improve this, we tried to optimize the molding conditions by strengthening the compression filling ratio, etc., but the voids between the particles were slightly reduced, but the expansion ratio was as low as 20 times or less. Also, the appearance of the molded article was remarkably reduced, and a molded article in a mold similar to a new molded article could not be obtained.

[0006]

SUMMARY OF THE INVENTION The present invention has been completed in view of the above-mentioned problems of the prior art by conducting a long-term study, in particular, examining various conditions for re-granulated expanded particles. The problem is to reuse the re-granulated expanded particles of the used polyolefin resin, and to mass-produce industrially stably,
An object of the present invention is to provide a polyolefin-based resin-in-foam molded article having excellent fusion properties and recoverability, improved physical properties and appearance, and a method for producing the same.

[0007]

According to the present invention, there is provided a polyolefin-based resin-molded in-mold foamed article comprising a polyolefin-based resin-molded in-molded foam containing re-granulated foamed particles of a polyolefin-based resin. Is 80% or more, and the recovery rate is 75% or more. The mixing ratio of the re-granulated expanded particles is preferably 5 to 60% by volume of the molded body. Further, the closed cell rate of the re-granulated expanded particles is preferably 30 to 70%. Further, the ratio of the expansion ratio of the re-granulated expanded particles / the expansion ratio of the polyolefin resin pre-expanded particles is from 0.6 to 0.6.
1.3, and the average particle diameter is preferably 4 to 10 mm. In addition, the melting point of the re-granulated expanded particles is preferably -5 ° C to + 7 ° C. of the melting point of the polyolefin-based resin pre-expanded particles.

Further, in the method for producing a polyolefin resin in-mold molded article of the present invention, a mixed particle of a re-granulated polyolefin resin particle and a polyolefin resin pre-expanded particle is filled in a mold and heated. Expand the foam particles,
In the method for producing a foamed molded article in a polyolefin-based resin mold which is formed by fusing, the method of (1) filling the mixed particles into a mold is as follows. Compression-filling the mixed particles into a mold with pressurized air, or filling the mold with the mixed particles, closing the mold and compressing the mixture; 5 to 60% by volume of the molded body,
(3) The closed cell ratio of the re-granulated expanded particles is 30 to 70%, and (4) the ratio of the expansion ratio of the re-granulated expanded particles / the expansion ratio of the polyolefin resin pre-expanded particles is 0.6 to 1. .
3, and the average particle size of the re-granulated expanded particles is 4 to 10.
mm, and (5) the re-granulated expanded particles have a melting point of −5 ° C. to + 7 ° C. of the melting point of the polyolefin resin pre-expanded particles. In this production method, the heating performed in the mold is preferably steam heating at a temperature of + 1 ° C. to + 14 ° C., which is the higher of the melting points of the re-granulated expanded particles and the pre-expanded particles.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described in detail. About "Polyolefin Resin" Polyolefin resins are low-, medium-, high-density polyethylene, linear low-density polyethylene, metallocene-catalyzed polyethylene, ethylene-based resins represented by ethylene-vinyl acetate copolymer, etc. The base resin is a random or block copolymer resin with propylene in which the polymerization component is one or more of ethylene, butene-1, 4-methylpentene-1, and the like, or a mixed resin in which two or more of these are blended. Which may be crosslinked or non-crosslinked. Regarding "the fusion rate between foamed particles is 80% or more" If the fusion rate between foamed particles of the polyolefin-based resin molded article is not 80% or more, mechanical properties such as compressive strength and tensile strength are exhibited. Therefore, the function of the buffer material is not satisfied. The preferred range of the fusion rate is 82% or more, more preferably 85% or more.

Regarding "Recovery rate of 75% or more" The recovery rate of the polyolefin resin molded article in the foam is 75%.
Otherwise, the repetition durability (repeated useability), which is a feature of the polyolefin-based resin molded article, will not be sufficient. The recovery rate is preferably at least 80%, more preferably at least 82%. Regarding "mixing ratio of re-granulated expanded particles: 5 to 60%" A high mixing ratio is desirable from the viewpoint of reuse. However, basically, as the mixing ratio of re-granulated expanded particles increases, quality, performance, and the like gradually decrease. Therefore, up to 60% is a preferable range for practical use. More specifically, if it exceeds 60%, the moisture content when taken out of the mold during in-mold molding gradually increases, and as a result, the drying time becomes longer and the productivity is reduced. In addition, the dimensional shrinkage ratio with respect to the mold also increases, and the dimensional accuracy (variation) deteriorates. As a result, the appearance quality and physical properties decrease. Therefore, the preferred range is up to 60%. The mixing ratio is preferably 5 to 50%, more preferably 5 to 40%.
%.

Regarding "closed cell ratio of 30 to 70%" Even if the mixing ratio of the re-granulated expanded particles is 5 to 60%, if the closed cell ratio is less than 30%, the quality, performance, especially the buffering performance An in-mold molded article having excellent properties cannot be obtained. On the other hand, it is technically difficult to increase the closed cell rate to more than 70%. It is said that the upper limit of the closed cell rate of the re-granulated expanded particles obtained by using a usual in-mold expanded molded article pulverizer is about 50%. Since the bubbles on the surface of the re-granulated particles are destroyed in the pulverizing step, the closed cell ratio is inevitably low. In particular, as the average particle diameter decreases, the surface area ratio per volume of one particle increases, so that the ratio of broken closed cells increases and the closed cell ratio decreases. The closed cell rate is preferably 35% or more, more preferably 40% or more.

By the way, the present inventor has found a technique for separately increasing the closed cell rate of the re-granulated expanded particles in the process of completing the present invention. The details will be described below. <Technology for increasing the closed cell ratio> The re-granulated foamed particles are subjected to instantaneous heat treatment of the particle surface with hot air near its melting point, preferably at a melting point of −7 ° C. to + 2 ° C., so that substantially closed cells are obtained. The rate is improved. For example, a cross-linked polyethylene in-mold molded article (Mef LD, trade name; Asahi Kasei Corporation)
Of re-granulated foam particles having a closed cell ratio of 27% and a melting point of 117 ° C. and a magnification of 30 cm ³ / g) were converted to 110 ° C.
As a result of processing for several seconds in a fluidized bed dryer using hot air of
The closed cell rate was greatly improved up to 60%. It is preferable to use the re-granulated expanded particles which have been subjected to the heat treatment to increase the closed cell ratio. Using this technique, the closed cell rate of the re-granulated expanded particles obtained by using a pulverizer can be increased to about 70%.

Regarding "the ratio of the expansion ratio of the re-granulated expanded particles / the expansion ratio of the pre-expanded particles is 0.6 to 1.3, and the average particle size of the re-granulated expanded particles is 4 to 10 mm" If the expansion ratio (ie, the value obtained by dividing the volume by the weight (cm ³ / g)) of the re-granulated expanded particles and the pre-expanded particles is largely different, the specific gravity difference between the expanded particles and the pre-expanded expanded particles increases. If the particles are pressure-fed and filled into the mold by air, the floating speed of the two will shift in the mold, resulting in non-uniform filling, making it impossible to obtain a uniform molded body. And even if the expansion ratio of both is in the above range, the average particle diameter of the re-granulated expanded particles is 4 to 1
It needs to be 0 mm. The in-mold foam molded article of the present invention used for the cushioning material generally has a complicated shape along the outer shape of the article to be packaged, and the thickness is generally distributed from 6 mm to 50 mm. Therefore, when the average particle size is 10
If it exceeds mm, defective filling in the mold cavity occurs partially, and the mold reproducibility of the in-mold foam molded article deteriorates. On the other hand, if the average particle diameter is less than 4 mm, the generation of fine particles and powder during re-granulation processing increases, and about 30% or more of the used buffer material cannot be reused, resulting in a problem of poor economic efficiency.

Regarding "the melting point of the re-granulated expanded particles is from -5 ° C. to + 7 ° C. of the melting point of the pre-expanded particles" Currently, polyolefin resin buffer materials generally used are crosslinked and non-crosslinked. There are cross-linking types, and various types of resins are used, such as low-density polyethylene, high-density polyethylene, linear low-density polyethylene, and random copolymers of ethylene and propylene. The melting points of these re-granulated expanded particles often have a large difference from each other. On the other hand, used polyolefin resin buffer materials generate a large amount of various types at the time of unpacking at the distribution process, for example, at wholesalers and home electronics mass retailers, and at this time, only the same type is sorted out and collected. Since this is not commercially viable, the re-granulated expanded particles necessarily contain different types of materials. In this case, a difference between the melting point of the re-granulated expanded particles and the melting point of the pre-expanded particles cannot be avoided. By the way, the melting point of the re-granulated expanded particles made of the different polyolefin resin is -5 of the melting point of the pre-expanded particles.
If the temperature is not in the range of ° C to + 7 ° C, an in-mold foam excellent in appearance and performance cannot be obtained. That is, when the melting point of some of the re-granulated expanded particles is out of the above temperature range, the particles expand,
Insufficient expansion results in a large number of large voids between particles or no fusion, or excessive heating results in the worst case of resinification and fusion to the mold.

Regarding "Method of Manufacturing Polyolefin-Based Resin-In-Mold Foam Molded Body" As described above, polyolefin-based resins are
The gas permeability of volatile foaming agents such as aliphatic hydrocarbons such as pentane and fluorocarbons is extremely large, and therefore, the foaming agent does not remain in the pre-expanded particles as well as the re-expanded expanded particles. In the heating step during molding, foaming and expansion properties cannot be expected. Therefore, any one of the following (a) to (c) is used so that a polyolefin-based resin in-mold foam having excellent physical properties and appearance quality can be obtained by the heating step in the in-mold molding. .

(A) Intra-bubble pressure application treatment In order to exhibit the same heat-foaming and expanding action as the foaming agent,
The mixed particles are stored in a pressurized container, and the pressure is 0.3 to 0.9M.
Hold under pressurized air of Pa (gauge pressure) for 1 to 18 hours,
Air is impregnated in the mixed particle bubbles to increase the pressure in the bubbles. In this case, to reduce the processing time, 40 to 8
It is also possible to carry out under heating at 0 ° C. The internal bubble pressure of the treated mixed particles is 0.02 to 0.2 in consideration of the expansion ratio of the pre-expanded particles and the re-granulated expanded particles and the mixing ratio of the both.
MPa (gauge pressure) is preferable, and if it is less than 0.02 MPa (gauge pressure), the molded product having insufficient internal pressure of the cell and having sufficient appearance quality and compressive strength and recovery performance sufficient for practical use cannot be obtained. . 0.2MPa (gauge pressure)
Exceeding the temperature causes excessive foaming and expansion in the heating step, so that heated steam does not flow between the foamed particles at the center of the mold, and the foamed particles do not fuse with each other.

(B) Compression filling in a mold with pressurized air A method of compressing mixed particles with pressurized air, filling the mixed particles in a compressed state into a mold under pressure, and then releasing the atmosphere to the atmosphere. is there. This method does not require the device described in (a) above.
A practical method is preferable because the auxiliary equipment (pressurizing hopper for filling) of the molding machine can be used as it is. In consideration of the expansion ratio of the pre-expanded particles and the re-granulated expanded particles, the mixing ratio of the both, and the like, the compression state of the mixed particles is set to 90 to 60% with respect to the original apparent bulk volume. What is necessary is just to adjust the pressure of a pressure hopper and the mold internal pressure. If the compression state of the mixed particles exceeds 90%, the effect of compression filling cannot be obtained, and the obtained molded article lacks the appearance quality. In a compressed state of less than 60%, the mixed particles are excessively filled in the mold. As a result, there is almost no void between the foamed particles, and the heated steam does not flow to the center of the mold, so that the heating of the foamed particles becomes insufficient and the fusion property between the foamed particles is reduced. The pressure of the filling hopper and the inner pressure of the mold may be the same, but it is more preferable to increase the former by about 0.01 to 0.04 MPa from the viewpoint of filling properties.

(C) Compression filling with mold opening The foaming particles are filled in the mold while the mold is opened by an amount corresponding to the volume of the void between the foaming particles, and the mold is closed to a regular position after the filling is completed. . The mold opening amount at the time of filling is an amount represented by the following formula, in consideration of the expansion ratio of the pre-expanded particles in the mixed particles, the expansion ratio of the re-granulated expanded particles, and the mixing ratio thereof,
A range of 10 to 50% is preferred.

(Equation 1) When the molded product has a thickness distribution, the thickest value is defined as the molded product thickness.

"The heating performed in the mold is performed at + 1 ° C. to + 10 ° C., which is the higher of the melting points of the re-granulated expanded particles and the pre-expanded particles.
If the heating in the mold exceeds the above range, that is, if it is less than + 1 ° C, the foaming and expansion of the particles will be partially insufficient, causing voids between the particles, Is insufficient, and the required properties of the molded article in the mold are deteriorated. Conversely, +1
If the temperature exceeds 0 ° C., the dimensional shrinkage and sink mark of the molded article become remarkable due to excessive heating, and the compressive strength is extremely deteriorated.

Next, a method for evaluating the properties of the foamed molded article in a polyolefin resin mold of the present invention will be described. (Characteristics of expanded particles) 1) Expansion ratio (magnification): Weight (g) The volume (cm ³ ) of a known expanded particle is measured by a submersion method (definition:...)
The value obtained by dividing the volume by the weight is defined as the expansion ratio (cm ³ / g). 2) Closed cell ratio: The true volume of about 24 cm ³ of expanded particles of known expansion ratio (cm ³ / g) and weight was measured using an air comparison type hydrometer 1000 manufactured by Tokyo Science Co., Ltd. ) To calculate and evaluate the closed cell rate S (%).

(Equation 2) Vx: volume of the true foamed particles (cm
³ ) Va: Volume of expanded particles [expansion ratio × weight] (cm ³ )

3) Melting point: Measured using a differential scanning calorimeter DSC7 manufactured by PerkinElmer. Expanded particles 1-6m
g from 30 ° C. at a rate of 10 ° C./min.
The temperature was raised to 00 ° C., and when the temperature reached 200 ° C., it was left for 30 seconds. After the temperature was lowered at a rate of 10 ° C./min to 30 ° C., a second melting operation was performed in the same manner, and a second melting operation was performed. The temperature of the maximum melting peak of is defined as the melting point. 4) Average particle diameter: The lengths of the minor axis and major axis of each particle were measured from about 30 expanded images of the foamed particles magnified 30 times using a magnifying projector, and the average value was divided by a magnifying power of 30. The value is defined as the average particle size.

(Characteristics of In-Mold Mold) 5) Fusing Ratio: A cut having a depth of about 1 mm is made in the thickness direction of the in-mold molded body, and the cut is made outward to bend and break. With respect to the total length in the thickness direction and the total number of particles having an area over a length of about 75 mm in this fractured surface, the number of foamed particles that are broken (material is broken) is evaluated by percentage. 6) Recovery rate: The molded product in the mold was subjected to a compression tester Autograph AG-5000D manufactured by Shimadzu Corporation at 10 mm /
75% of the thickness (approx.
Immediately after compression, the load is removed at the same speed until the load becomes zero, the thickness at the moment when the load becomes zero is measured, and the recovery rate R (%) is calculated and evaluated from the following equation (2).

(Equation 3) T ₀ : Thickness before test (mm) T ₁ : Thickness after test (when load is zero) (mm) 7) Expansion ratio; weight (g) Volume of known in-mold molded product (c)
m ³ ) is measured by the submersion method, and the value obtained by dividing the volume by the weight is defined as the expansion ratio (cm ³ / g).

8) Variation in Foaming Ratio Twenty-five test pieces having a width and length of 50 mm were cut out from the molded product in the mold, and the foaming ratio (cm ³ / g) was measured in the same manner as in 7). 3) Calculate and evaluate the variation X (%) of the expansion ratio from the above.

(Equation 4) E _X: the average value of expansion ratio _{^{(cm 3 / g) E max}} : maximum value of the expansion ratio _{^{(cm 3 / g) E min}} : minimum value of expansion ratio (cm ³ / g)

[0024]

[Table 1]

9) Compressive strength: a stress at the time of compressing an in-mold molded article at a compression speed of 10 mm / min using a compression tester Autograph AG-5000D manufactured by Shimadzu Corporation. The lower stress is defined as the compressive strength and JIS
It is evaluated by the test method of Z-0235. 10) Moisture content; immediately remove moisture adhering to the surface of the in-mold molded body obtained by demolding from the in-mold molding machine, measure the weight after 2 minutes at room temperature, and then measure the hot air at 80 ° C. After leaving it to dry for 8 hours in a circulating thermostat, take it out to room temperature and remove it for 2 hours.
After being left for 4 hours, the weight was measured, and the water content W was calculated from the following equation (4).
(Vol%) is calculated and evaluated.

(Equation 5) W ₀ : weight before drying (g) W ₁ : weight after drying (g) V: inner volume of the mold 2250 cm ³ (inner dimensions 30 cm × 30)
cm × 2.5cm)

[0026]

[Table 2] 11) Appearance quality: The degree of dents generated between the foamed particles on the surface of the molded article in the mold and the occurrence of wrinkles are visually observed and evaluated.

[0027]

[Table 3] Hereinafter, the content of the present invention will be described in detail with reference to Examples, but these do not limit the scope of the present invention.

[0028]

Examples 1-5, Comparative Examples 1-2 Thickness is 40-60 mm
Plate-shaped cross-linked polyethylene-in-foam molded product (MEF L
D, trade name; manufactured by Asahi Kasei Kogyo Co., Ltd., melting point 117 ° C., foaming ratio 30 cm ³ / g). After coarsely pulverizing with a crusher (coarse pulverizing blade 1) and then pulverizing with a granulator [(rotor 3 / screen 4 (screen hole diameter: 11 mm)), the aperture is 2.5 m.
The particles were classified with a filter of m to remove fine particles, and re-granulated expanded particles having an average particle diameter of 9.5 mm, an expansion ratio of 26 cm ³ / g, and a closed cell ratio of 52% were produced.

Next, the re-granulated expanded particles and unused cross-linked polyethylene pre-expanded particles (Mef LD, trade name; manufactured by Asahi Kasei Corporation), melting point 117 ° C., expansion ratio 32 cm ³
/ G), when the mixing ratio of the re-granulated expanded particles is 5%, 10%, 30%, 50%, and 60% by volume of the molded product (Examples 1 to 3).
5), 70% and 100% (Comparative Examples 1 and 2) were supplied to the mixing device at a ratio such that they became uniform mixed particles. Subsequently, the mixed particles were charged from a filling hopper with air into a molding die having a water vapor hole (cavity dimension: 30 cm × 3).
0 cm × 2.5 cmt) and filling in the mold by the above-mentioned mold opening compression filling method (mold opening width: 13.5 mm).
Then, heated steam (pressure: 0.128 M
Pa (gauge pressure), temperature: expanded particle melting point plus 7.5 ° C
= 124.5 ° C) and heated, and then cooled with water after molding to obtain an in-mold molded product.

[0030]

REFERENCE EXAMPLE 1 The same procedure as in Example 1 was carried out except that unused crosslinked polyethylene pre-expanded particles (Mef LD, trade name; manufactured by Asahi Kasei Kogyo Co., Ltd., melting point 117 ° C., expansion ratio 32 cm ³ / g) were used alone as the expanded particles. Molding was performed in the same manner as in Example 1 to produce an in-mold molded body. The obtained in-mold molded product was evaluated by the above evaluation method, and the results are shown in Table 1. According to the results in Table 1, the in-mold molded products of Examples 1 to 5 maintain a high level of fusion rate and recoverability with respect to Comparative Examples 1 and 2, and are excellent in appearance quality,
Further, the compressive strength also maintains a high level value, and it can be seen that there is almost no inferiority to Reference Example 1 using the pre-expanded particles alone.

[0031]

Examples 6 and 7, Comparative Examples 3 and 4 Non-crosslinked polyethylene in-mold foam (Mef NX, trade name; manufactured by Asahi Kasei Kogyo Co., Ltd., melting point 126 ° C.) used as a cushioning material for desktop personal computers , A foaming ratio of 45 cm ³ / g), and a crusher (coarse crushing part) / granulator (re-granulation part) shown in FIG. 1 (screen hole diameter: 8 m)
m), crushed with a filter having an aperture of 2.5 mm to remove fine particles, and regranulated foaming having an average particle size of 6.8 mm, an expansion ratio of 39 cm ³ / g, and a closed cell ratio of 36%. Particles were made. The re-granulated expanded particles and unused non-crosslinked polyethylene pre-expanded particles (Mef NX, trade name; manufactured by Asahi Kasei Corporation, melting point 126 ° C., expansion ratio 32 cm ³⁾
/ G) is 30%, 60% (Examples 6 to 7), 70%, 100% in terms of the volume ratio of the re-granulated expanded particles.
(Comparative Examples 3 and 4) The mixture was supplied to the mixing device at a ratio such that the mixture became uniform mixed particles. Subsequently, a molding die (cavity dimension: 30 cm × 30 cm × 2.5 cm) having a water vapor hole with air from the filling hopper with the mixed particles.
Into the mold, and filled in the mold by the above-described mold opening compression filling method (mold opening width: 5.5 mm), and then heated steam (pressure: 0.147 MPa (gauge pressure), temperature: expanded melting point plus (1 ° C. = 127 ° C.)
After molding, the resultant was cooled with water to obtain a molded article in a mold.

[0032]

Reference Example 2 The same procedure was carried out except that unused non-crosslinked polyethylene pre-expanded particles (Mef NX, trade name; manufactured by Asahi Kasei Kogyo Co., Ltd., melting point 126 ° C., expansion ratio 32 cm ³ / g) were used alone as the expanded particles. Molding was performed in the same manner as in Example 2 to produce an in-mold molded body. The obtained in-mold molded body was evaluated by the above evaluation method, and the results are shown in Table 2. According to the results in Table 2, the in-mold molded articles of Examples 6 to 7 maintain a high fusion rate and recoverability, are excellent in appearance quality, and have a high compressive strength as compared with Comparative Examples 3 and 4. It can be seen that it retains a high level value and is almost comparable to Reference Example 2 using pre-expanded particles alone.

[0033]

Examples 8 to 11 and Comparative Example 5 Discarded scraps of the foamed cross-linked polyethylene mold used in Example 1 were coarsely pulverized by a crusher (coarse pulverizing blade 1) shown in FIG. Pulverized by a granulator having a diameter of 6 mm, and classified by a filter having an aperture of 2.5 mm to obtain re-granulated expanded particles having an average particle diameter of 4.8 mm, an expansion ratio of 23 cm ³ / g, and a closed cell ratio of 27%. Was prepared. Next, the re-granulated expanded particles are subjected to a heat treatment for 5 to 15 seconds in a fluidized-bed dryer having a hot air temperature of 110 to 119 ° C., so that the closed cell ratio is 30 to 7
0% of expanded particles were obtained. Subsequently, the mixture ratio of the heat-treated re-granulated expanded particles and the unused cross-linked polyethylene pre-expanded particles used in Example 1 was 35% (by volume of the molded article).
, And an in-mold molded product was produced in the same manner as in Example 1. (Examples 8 to 11) On the other hand, molding was carried out in exactly the same manner except that heat-treated re-granulated expanded particles (having a closed cell ratio of 27%) were not subjected to heat treatment instead of the heat-treated re-granulated expanded particles. The body was made. (Comparative Example 5) The obtained in-mold molded product was evaluated by the evaluation method described in the text, and the results are shown in Table 3. According to Table 3, the in-mold molded article of the present invention has a small closed cell rate of the re-granulated expanded particles, and therefore has a low water content and an excellent appearance quality.

[0034]

Examples 12 to 15, Comparative Examples 6 and 7 The expansion ratio was 15,
20, 25, 30, 40, 50 cm ³ / g and a thickness of 50
mm of plate-shaped cross-linked polyethylene in-mold foamed molded product (Mef LD, trade name; manufactured by Asahi Kasei Kogyo Co., Ltd., melting point: 117 ° C) is roughly crushed by a crusher (coarse crushing blade 1) shown in FIG. Thereafter, the mixture was pulverized with a granulator having a screen hole diameter of 8 mm, and classified with a filter having an aperture of 2.5 mm to remove fine particles.
Re-granulated expanded particles of 4, 33, and 42 cm ³ / g were produced. The closed cell ratio was 35 to 65%. Then
Each of the re-granulated expanded particles and unused cross-linked polyethylene pre-expanded particles (Mef LD, trade name; manufactured by Asahi Kasei Corporation)
A melting point of 117 ° C. and a magnification of 26 cm ³ / g) were supplied to a mixing device and mixed so that the former mixing ratio (molded product volume ratio) was 30%.

Subsequently, an in-mold molded article was produced in the same manner as in Example 1 using the mixed particles. In addition, an in-mold molded article of the pre-expanded particles alone (Reference Example 3) was similarly produced. The obtained in-mold molded product was evaluated by the evaluation method described in the text, and the results are shown in Table 4. According to Table 4, the in-mold molded article of the present invention is:
It can be seen that the pre-expanded particles have substantially the same “expansion ratio variation” as the in-mold molded product of the pre-expanded particles alone (Reference Example 3). Thereby, the in-mold molded article of the present invention has excellent uniformity and almost the same function even when taking any part of the in-mold molded article,
In particular, it can be seen that it has a strength and a buffering action.

[0036]

[Table 4]

[0037]

[Table 5]

[0038]

[Table 6]

[0039]

[Table 7]

[0040]

According to the present invention, a polyolefin having excellent physical properties such as recoverability and compressive strength and having improved appearance quality is reused by recycling the re-granulated expanded particles of the used polyolefin resin foam. Because the resin molded in-mold mold can be mass-produced in an industrially stable manner,
The social significance is extremely large from the viewpoint of environmental conservation.

[Brief description of the drawings]

FIG. 1 is a side view of an apparatus for re-granulating a used buffer material, which includes a crusher (coarse crushing blade 1) and a granulator (rotor 3 / screen 4).

FIG. 2 is a front view of the re-granulation apparatus.

[Explanation of symbols]

 1: Coarse pulverizing blade 2: Coarse pulverizing part 3: Rotor 4: Screen 5: Granulator (re-granulation part) 6: Re-granulated expanded particle take-out port 7: Screen hole 8: Drive unit

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[Procedure amendment]

[Submission date] June 20, 2000 (2006.2.
0)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0020

[Correction method] Change

[Correction contents]

Next, a method for evaluating the properties of the foamed molded article in a polyolefin resin mold of the present invention will be described. (Characteristics of Expanded Particles) 1) Expansion ratio (magnification): Weight (g) The volume (cm ³ ) of a known expanded particle was measured by a submerged method, and the value obtained by dividing the volume by weight was used as the expansion ratio (cm ³ / cm). g). 2) Closed cell ratio: The true volume of about 24 cm ³ of expanded particles of known expansion ratio (cm ³ / g) and weight was measured using an air comparison type hydrometer 1000 manufactured by Tokyo Science Co., Ltd. ) To calculate and evaluate the closed cell rate S (%).

(Equation 2) Vx: volume of the true foamed particles (cm
³ ) Va: Volume of expanded particles [expansion ratio × weight] (cm ³ )

 ────────────────────────────────────────────────── ─── Continued on the front page F term (reference) 4F074 AA17A AA17B AA18 AA19 AA20 AA21 AA22A AA22B AA24A AA24B AA25A AA25B AB03 BA33 BA34 BA84 CA24 CA51 CC03X CC04X CC05Z CC12Y CC34XCC47 CC03 CD07 A02 DA03 A02 DA03 A UF21 UW45

Claims (7)

[Claims] 1. A polyolefin-based resin molded article containing particles obtained by pulverizing an in-mold molded article of polyolefin-based resin expanded particles (hereinafter referred to as re-granulated expanded particles). A foamed molded article in a polyolefin-based resin mold having a deposition rate of 80% or more and a recovery rate of 75% or more. 2. The expanded molded article in a polyolefin-based resin mold is composed of re-granulated expanded particles and polyolefin-based resin pre-expanded particles, and the mixing ratio of the re-granulated expanded particles is determined by the volume ratio of the molded article. The foamed molded article in a polyolefin resin mold according to claim 1, wherein the content is 5 to 60%. 3. The closed cell rate of the re-granulated expanded particles is from 30 to 30.
The foamed molded article in a polyolefin-based resin mold according to claim 1 or 2, which is 70%. 4. The ratio of the expansion ratio of the re-granulated expanded particles / the expansion ratio of the polyolefin-based resin pre-expanded particles is from 0.6 to 1.
3, and the average particle size of the re-granulated expanded particles is 4 to 10.
The polyolefin-based resin-molded in-mold foamed product according to any one of claims 1 to 3, wherein 5. The polyolefin-based resin according to claim 1, wherein the re-granulated expanded particles have a melting point of −5 ° C. to + 7 ° C. of the melting point of the polyolefin-based resin pre-expanded particles. In-mold foam molding. 6. A polyolefin-based resin in-mold foaming method in which mixed particles of re-granulated foamed particles and polyolefin-based resin pre-expanded particles are filled in a mold and heated to expand and fuse the foamed particles with each other. In the method for producing a body, (1) the method of filling the mixed particles into a mold includes filling the mixed particles into the mold after applying the internal pressure to the bubbles, or compressing and filling the mixed particles into the mold with pressurized air. Alternatively, it is either a method of filling the mixed particles in a mold, closing the mold and compressing,
(2) The mixing ratio of the re-granulated expanded particles is 5 by volume ratio of the molded body.
(3) the closed cell rate of the re-granulated expanded particles is 30 to 70%, and (4) the expansion ratio of the re-granulated expanded particles / the expansion ratio of the polyolefin resin pre-expanded particles. The ratio is 0.6 to 1.3, and the average particle size of the re-granulated expanded particles is 4 to 10 mm. (5) The melting point of the re-granulated expanded particles is the melting point of the polyolefin resin pre-expanded particles. A method for producing a polyolefin-based resin molded foam inside, which is at -5 ° C to + 7 ° C. 7. The heating performed in the mold is steam heating at a temperature of + 1 ° C. to + 10 ° C., which is the higher value of the melting points of the re-granulated expanded particles and the polyolefin-based resin pre-expanded particles. Item 7. The method for producing a polyolefin resin in-mold foamed article according to Item 6.