JP2005306015A - Continuously manufacturing method of foamed polyolefinic resin molding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve productivity by raising a line speed, or reduce the size of an apparatus and further produce a good foamed molding desired by avoiding abnormal expansion causing deformation of the foamed molding obtained, in a method for continuously manufacturing a foamed molding comprising the step of feeding polyolefinic resin foamed particles to the space between endless belts continuously moving along the upper and lower faces in a path way surrounded with a structural member and having a rectangular cross-section. <P>SOLUTION: It is used that the foamed polyolefinic particles having a compound structure formed by a core layer being a foamed state made of a crystalline polyolefinic resin and a coating layer being substantially not foamed state consisted of a polyolefinic resin with a melting temperature lower by at least 15°C than the melting temperature of the polyolefinic resin forming the core layer or a polyolefinic resin with a Vicat softening temperature lower by at least 15°C than the Vicat softening temperature of the polyolefinic resin forming the core layer. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for continuously producing a plate-like foamed molded article using polyolefin resin expanded particles.

Foamed molded articles of polyolefin resins such as polyethylene resins and polypropylene resins are suitably used as cushioning materials because of their excellent chemical resistance, excellent buffering properties and resistance to chipping.
Using polyolefin resin expanded particles, polyolefin resin expanded particles are continuously supplied between endless belts that run along the upper and lower surfaces in a rectangular passage, and the polyolefin resin expanded particles are heated. For example, Patent Document 1, Patent Document 2, Patent Document 3, Patent Document 4, Patent Document 5, or Patent Document 6 or the like is a method for continuously manufacturing a plate-like foamed molded article by sequentially passing through an area and a cooling area. Is known by.
Patent Document 1 and Patent Document 2 disclose that foamed particles are compressed and used for molding. Further, Patent Document 3 discloses that foamed particles having a compression recovery rate represented by a specific mathematical expression are used for once compression, and then the compression is released for use in molding. Patent Documents 5 and 6 disclose a molding method including a step of reducing the bulk density of expanded particles.
However, the problems found in these methods require considerable time for cooling. As a result, if the line speed is slowed or the cooling zone is not lengthened, the resulting foamed molded product will be undercooled, After being taken out of the foamed product, the foamed molded product undergoes abnormal expansion and distortion occurs, making it difficult to obtain a desired good foamed molded product. If the line speed is slowed to eliminate the lack of cooling, productivity will be reduced and manufacturing costs will be affected. On the other hand, if the cooling zone is lengthened, the above-mentioned abnormal expansion of the foamed molded product can be prevented even if the line speed is increased. However, increasing the cooling zone lengthens the entire molding device and increases the cost of the molding device. Will be invited. In addition, when the molding apparatus must be installed in a limited space, there is a problem that the installation of the apparatus itself becomes difficult.
In the continuous molding method as described above, in Patent Document 4, the heating region in the molding apparatus is defined as the first heating region and the second heating region, and the steam supply direction is reversed between the first heating region and the second heating region. It is disclosed that the line speed is improved by doing so. However, specifically, in Example 4, the line speed is only 2.5 m / min with an apparatus having a cooling zone length of 6 m, which is still not sufficient from the viewpoint of improving productivity.

JP-A-9-104026 JP-A-9-104027 JP-A-10-180888 JP 2000-15708 A JP 2000-6253 A JP 2002-240073 A

  The present invention is a method for continuously producing a foamed molded product using polyolefin resin foamed resin particles by a molding apparatus as described above, and improving the line speed and improving the productivity, or An object of the present invention is to reduce the size of the apparatus, and to prevent the abnormal expansion that causes deformation of the obtained foamed molded product and to produce a desired good foamed molded product.

That is, the present invention
(1) Polyolefin resin foam particles are supplied between endless belts that continuously move along the upper and lower surfaces in a passage having a rectangular cross section surrounded by a structural material. In the method for continuously producing a foamed molded article by sequentially passing the resin foam particles through the heating region and the cooling region, as the polyolefin resin foam particles, a foamed core layer composed of a crystalline polyolefin resin, and a core A substance comprising a polyolefin polymer having a melting point of 15 ° C. or more lower than the melting point of the polyolefin resin forming the layer, or a polyolefin polymer having a Vicat softening point of 15 ° C. or more lower than the Vicat softening point of the polyolefin resin forming the core layer Characterized in that it uses expanded particles having a composite structure composed of a non-foamed coating layer The continuous process resin foamed molded,
(2) The method for continuously producing a polyolefin resin foam molded article according to (1), wherein the foamed particles are foamed particles to which an internal pressure of 0.03 to 0.35 MPa (G) is applied. ,
(3) The temperature of the forming steam supplied in the heating region is the melting point (MPc (° C)) of the polyolefin resin forming the core layer of the expanded particles when the polyolefin polymer forming the coating layer exhibits a melting point. ) And the melting point (MPs (° C.)) of the polyolefin polymer forming the coating layer, when the temperature is not lower than MPs and lower than MPc, and the polyolefin polymer does not exhibit a clear melting point, the expanded particles Based on the melting point (MPc (° C.)) of the polyolefin resin forming the core layer and the Vicat softening point (VSPs (° C.)) of the polyolefin polymer forming the coating layer, [VSPs + 10 ° C.] or more and less than MPc A method for continuously producing a polyolefin resin foam molded article according to the above (1) or (2),
(4) The continuous production method of a polyolefin resin foam molded article according to any one of the above (1) to (3), wherein the polyolefin polymer comprises a polyethylene polymer having a melting point of 125 ° C. or lower,
Is the gist.

  The present invention relates to a foamed core layer composed of a crystalline polyolefin-based resin, and a polyolefin-based material that has a melting point of 15 ° C. or more lower than the melting point of the polyolefin-based resin that forms the core layer, or that forms a core layer. By using foamed particles having a composite structure composed of a substantially non-foamed coating layer made of a polyolefin-based polymer having a Vicat softening point of 15 ° C. or more lower than the Vicat softening point of the resin, (a) In the case of a molding apparatus having a cooling zone having the same length as the above, even if the line speed is increased, the resulting foamed molded product is not deformed due to abnormal expansion, and as a result, productivity can be increased. (b) On the other hand, when the line speed is the same as before, the foamed molded product obtained even if the cooling zone is shortened does not deform due to abnormal expansion, and the overall length of the manufacturing apparatus can be shortened. In addition, the compactness of the molding apparatus can be achieved, the cost of the apparatus can be reduced, and the site space can be effectively used.

  The present invention relates to a foamed particle having a composite structure composed of a foamed core layer made of a crystalline polyolefin resin and a substantially non-foamed coating layer made of a polyolefin polymer. This is a method for producing a foamed molded article using a continuous molding apparatus.

One of the features of the present invention is that the polyolefin resin expanded particles used have a foamed core layer made of a crystalline polyolefin resin and a melting point of 15 ° C. or higher than the melting point of the polyolefin resin forming the core layer. A composite structure comprising a low polyolefin polymer or a substantially non-foamed coating layer comprising a polyolefin polymer having a Vicat softening point of 15 ° C. or more lower than the Vicat softening point of the polyolefin resin forming the core layer In the expanded particles.
In the present specification, “foamed particles having a composite structure” may be simply referred to as “foamed particles”.

  Here, the crystalline polyolefin-based resin employs “when the melting temperature is measured after performing a certain heat treatment” described in JIS K7121 (1987) (the heating rate in adjusting the state of the test piece) (Cooling rate is 10 ° C / min in all cases) When using a heat flux differential scanning calorimeter (hereinafter referred to as “DSC device”) and drawing a DSC curve at a heating rate of 10 ° C / min. The polyolefin resin which shows the melting peak (endothermic peak) accompanying melting of resin to the obtained DSC curve is meant.

  Examples of the crystalline polyolefin resin that forms the core layer of the expanded particles used in the present invention include polypropylene resin, polyethylene resin, polybutene resin, and polymethylpentene resin. A polypropylene-based random copolymer or a polypropylene-based block copolymer obtained from a polymer, α-olefin other than propylene and propylene, and / or ethylene is preferable.

  Here, the polyolefin resin is an olefin homopolymer in which 50 mol% or more of structural units obtained from olefin are present, preferably 60 mol% or more, more preferably 80 mol% to 100 mol%. It means a copolymer of the above olefins, a copolymer of an olefin and another monomer, a mixture of two or more of these, or a mixture of one or more of these and another polymer. Similarly, the polypropylene-based resin is a propylene homopolymer in which a structural unit obtained from propylene is present in an amount of 50 mol% or more, preferably 60 mol% or more, more preferably 80 mol% to 100 mol%, and propylene. A copolymer with another monomer, or a mixture of two or more of these may be mentioned.

  Similarly, the polyethylene-based resin is an ethylene homopolymer in which a structural unit obtained from ethylene is 50 mol% or more, preferably 60 mol% or more, more preferably 80 mol% to 100 mol%, ethylene and A copolymer with another monomer, or a mixture of two or more of these may be mentioned.

  In the present invention, other thermoplastic polymers may be mixed with the polyolefin resin such as the polypropylene resin and polyethylene resin within a range that does not impair the object of the present invention. The amount of the other thermoplastic polymer added is preferably 100 parts by weight or less, more preferably 50 parts by weight or less, still more preferably 30 parts by weight or less, and particularly preferably 15 parts by weight with respect to 100 parts by weight of the polyolefin resin. Or less, most preferably 5 parts by weight or less.

  Further, the crystalline polyolefin resin forming the core layer may contain additives such as a catalyst neutralizing agent, a lubricant, a crystal nucleating agent, and an antioxidant as necessary. The amount of the additive added (excluding those that eventually disappear after evaporating like a foaming agent) depends on the type of additive and the purpose of use, but with respect to 100 parts by weight of the crystalline polyolefin-based resin, The amount is preferably 40 parts by weight or less, more preferably 30 parts by weight or less, and still more preferably 0.001 to 15 parts by weight.

  The crystalline polyolefin-based resin preferably has a melting point (Tm) of 100 ° C. to 250 ° C., more preferably 110 ° C. to 170 ° C., more preferably 120 ° C. to 120 ° C. in consideration of thermal processability and heat resistance. The thing of 160 degreeC is especially preferable. The crystalline polyolefin-based resin preferably has a Vicat softening point of 70 ° C to 200 ° C, more preferably 90 ° C to 160 ° C, and particularly preferably 110 ° C to 150 ° C.

The melting point (Tm) is a value determined as the peak temperature of the melting peak on the DSC curve obtained by drawing a DSC curve using the DSC apparatus at a heating rate of 10 ° C./min.
If a plurality of melting peak vertices are observed on the DSC curve, the melting point is the vertex temperature of the melting peak having the highest melting peak with reference to the high temperature side baseline. Moreover, when there are a plurality of melting peaks showing the highest vertex, the arithmetic average value thereof is taken as the melting point. The Vicat softening point is a Vicat softening point measured by the A50 method based on JIS K7206 (1999).

  Further, the melting point of the polyolefin-based polymer forming the coating layer of the expanded particles used in the present invention is also measured by the above method. The polyolefin polymer forming the coating layer includes the case where the melting point does not substantially show the melting point. “No substantial melting point” refers to a case where no clear melting peak is exhibited when measured by the same method as the above melting point (Tm) measurement method. In the case where no clear melting peak is shown, the maximum heating temperature in the condition adjustment of the test piece by measurement with a heat flow DSC apparatus is up to 220 ° C.

  In the foamed particles used in the production method of the present invention, the polyolefin polymer forming the coating layer is a crystalline polyolefin that forms the core layer when the polyolefin polymer exhibits a clear melting peak. It is necessary that the melting point is 15 ° C. or more lower than the melting point of the resin. When the polyolefin polymer does not show a clear melting peak, it is necessary that the Vicat softening point is lower by 15 ° C. or more than the Vicat softening point of the crystalline polyolefin resin forming the core layer. The lower limit of the clear melting peak is 2 J / g.

In the production method of the present invention, the polyolefin polymer forming the coating layer as expanded particles is composed of a polyolefin polymer whose melting point or Vicat softening point is lower by 15 ° C. or more than the crystalline polyolefin resin forming the core layer. By using the expanded particles having the composite structure, the cooling time in the molding process can be shortened, and abnormal expansion that causes deformation of the molded foam after molding can be prevented.
This is considered to be due to the fact that the expanded particles used in the present invention can be fused with each other at a relatively low heating temperature in the heating region in the production method of the present invention.

  In the expanded particles used in the present invention, when the polyolefin polymer forming the coating layer has a clear melting point, the melting point is 15 ° C. or more higher than the melting point of the crystalline polyolefin resin forming the core layer. It is required to be low, and the melting point is preferably 20 ° C. or more, more preferably 20 ° C. to 60 ° C., and even more preferably 20 ° C. to 40 ° C.

  Further, when the polyolefin polymer forming the coating layer does not exhibit a clear melting point, it is required to be at least 15 ° C. lower than the Vicat softening point of the crystalline polyolefin resin forming the core layer, and 20 ° C. The Vicat softening point is preferably low, more preferably 20 ° C to 60 ° C, and particularly preferably 20 ° C to 40 ° C.

  On the other hand, when considering the heat resistance of the foamed molded article, the melting point of the polyolefin polymer forming the coating layer is preferably 60 ° C. or higher, more preferably 70 ° C. or higher, still more preferably 80 ° C. or higher, and 90 ° C. or higher. Is most preferred. The Vicat softening point of the polyolefin polymer forming the coating layer is preferably 50 ° C. or higher, more preferably 60 ° C. or higher, still more preferably 70 ° C. or higher, and most preferably 80 ° C. or higher.

  In the expanded particles used in the present invention, the difference between the melting point or Vicat softening point of the crystalline polyolefin resin forming the core layer and the melting point or Vicat softening point of the polyolefin polymer forming the coating layer is 15 ° C. If it is smaller, the molding temperature must be set high for fusion between the expanded particles, and in order to prevent abnormal expansion after molding, it is necessary to lengthen the cooling time as a result of the present invention. It is difficult to achieve one of the objectives.

  As described above, the polyolefin-based polymer forming the coating layer in the expanded particles used in the present invention includes those exhibiting a melting point and those not substantially exhibiting a melting point. Examples of the melting point include high-pressure low-density polyethylene resin, linear low-density polyethylene resin, linear ultra-low-density polyethylene resin, vinyl acetate, unsaturated carboxylic acid ester, unsaturated carboxylic acid, vinyl Examples thereof include a polyethylene copolymer resin obtained from a monomer such as alcohol and ethylene. The polyolefin polymer forming the coating layer satisfies the condition that the melting point is 15 ° C. or more lower than that of the crystalline polyolefin resin forming the core layer when the polyolefin polymer has a clear melting point. As long as the polyolefin polymer having a melting point for forming the coating layer is used, it may be a polypropylene resin or a polybutene resin.

  Examples of the polyolefin-based polymer that does not substantially exhibit the melting point include rubbers such as ethylene-propylene rubber, ethylene-propylene-diene rubber, ethylene-acrylic rubber, chlorinated polyethylene rubber, and chlorosulfonated polyethylene rubber, An elastomer is mentioned. These polyethylene rubber-like polymers can be used as two or more types of compositions in addition to single use.

  If necessary, other polymers can be added to the polyolefin polymer forming the coating layer. In this case, the amount of the other polymer added is desirably a small amount within the range not impairing the object of the present invention, and is preferably 100 parts by weight or less, more preferably 50 parts by weight with respect to 100 parts by weight of the polyolefin-based polymer. Or less, more preferably 30 parts by weight or less, particularly preferably 15 parts by weight or less, and most preferably 5 parts by weight or less. Further, the polyolefin polymer forming the coating layer may contain additives such as a catalyst neutralizing agent, a lubricant, a crystal nucleating agent, and an antioxidant. Although the amount of the additive depends on the type of additive, it is preferably 40 parts by weight or less, more preferably 30 parts by weight or less, and still more preferably 0. 0 part by weight with respect to 100 parts by weight of the polyolefin polymer. 001 to 15 parts by weight is preferable.

  In the present invention, a polymer composition obtained by mixing the polyolefin polymer forming the coating layer with the same crystalline polyolefin resin as the core layer can also be suitably used. According to such a polymer composition, when the core layer and the coating layer are difficult to thermally bond to each other, there is an advantage that the adhesion between the core layer and the coating layer is improved.

  The blending amount of the same crystalline polyolefin resin as the core layer mixed with the polyolefin polymer forming the coating layer is 1 to 100 parts by weight with respect to 100 parts by weight of the polyolefin polymer. The amount is preferably 80 parts by weight, and more preferably 5 to 50 parts by weight. If the blending ratio of the same crystalline polyolefin resin as the core layer is too large, the crystalline polyolefin resin tends to form a continuous phase (sea phase). Adhesion becomes insufficient, and as a result, the cooling time must be lengthened, which is not preferable.

Among the polyolefin-based polymers forming the coating layer, a high-pressure method low-density polyethylene resin and a linear low-density polyethylene resin are preferable. As the linear low-density polyethylene resin, for example, a linear low-density polyethylene resin (hereinafter referred to as MeLLDPE) polymerized using a metallocene polymerization catalyst is preferable.
In the present invention, a foamed core layer made of a polypropylene resin having a melting point of 120 ° C. to 165 ° C., and a melting point of 125 ° C. or less, preferably 90 ° C. to 125 ° C., more preferably 95 ° C. to 120 ° C. A combination using a polyethylene polymer as a coating layer is particularly desirable.
However, in this case, the polyethylene polymer needs to have a melting point 15 ° C. or more lower than that of the polypropylene resin. In this case, MeLLDPE is preferable as the polyethylene polymer for forming the coating layer. Usually, a polyethylene polymer tends to be hard to be thermally bonded to a polypropylene resin, but MeLLDPE is excellent in thermal adhesiveness to a polypropylene resin. For this reason, when producing expanded particles having a composite structure, an effect is obtained in which separation between the core layer and the coating layer is difficult. In addition, MeLLDPE has a high heat resistance despite its low melting point, and therefore has an advantage that it is difficult to cause so-called blocking in which foamed particles are thermally fused during production of foamed particles. Although these reasons are not clear, the molecular weight distribution of the polymer by the metallocene polymerization catalyst is narrow, and it is caused by the fact that the low molecular weight component is not contained or is contained in a trace amount. Guessed. The density of MeLLDPE will usually be in a range of 0.890~0.935g / cm ^3, preferably in the range of 0.898~0.920g / cm ^3.

  In the expanded particle of the present invention, as the polypropylene resin forming the core layer, a structural unit obtained from propylene is 100 to 85 mol%, ethylene and / or an α-olefin having 4 to 20 carbon atoms. Is preferably a propylene homopolymer or a polypropylene-based copolymer with 0 to 15 mol% or less. Specific examples of the comonomer ethylene and / or α-olefin having 4 to 20 carbon atoms used in the production of the polypropylene-based copolymer include 1-butene, 1-pentene, 1-hexene, 1-octene, 4-methyl-1-butene and the like can be mentioned.

  The polypropylene resin contains 85 mol% to 98 mol% of a structural unit obtained from propylene in the polypropylene resin, and is a structural unit (comonomer of comonomer) obtained from ethylene and / or an α-olefin having 4 to 20 carbon atoms. More preferably, the structural unit is a propylene-based copolymer containing 2 to 15 mol%. When the proportion of the comonomer structural unit exceeds 15 mol%, the mechanical properties such as bending strength and tensile strength of the polypropylene resin forming the core layer are greatly reduced, and the mechanical properties of the resulting foam molded article are obtained. There is a risk of causing a decrease. Moreover, when the ratio of the structural unit of the comonomer in the polypropylene resin is 2 mol% or more, the foaming property is higher than that of less than 2 mol%, and excellent in low temperature molding at the time of molding.

In the polypropylene resin, the proportion of position irregular units based on 2,1-insertion of propylene monomer units in all propylene insertions measured by ¹³ C-NMR method is 0.5 to 2.0%, and propylene The ratio of the position irregular unit based on 1,3-insertion of the monomer unit is preferably 0.005 to 0.4%.
When the ratio of irregular position units based on 2,1-insertion is less than 0.5%, or when the ratio of position irregular units based on 1,3-insertion is less than 0.005%, When foamed particles using polypropylene resin as the base resin for the core layer are molded, the effect of reducing the compression set of the resulting foamed molded article is inferior.

On the other hand, when the ratio of the position irregular unit based on the 2,1-insertion exceeds 2.0%, or the ratio of the position irregular unit based on the 1,3-insertion exceeds 0.4%. The mechanical properties of the polypropylene resin as the base resin, such as bending strength and tensile strength, are lowered, and there is a possibility that the strength of the foamed particles and the foamed molded product obtained therefrom is lowered.
Such irregular units have the effect of lowering the crystallinity of the polypropylene resin, and show the effect of increasing the foamability of expanded particles using the polypropylene resin as a base resin for the core layer. In addition, a foamed molded article obtained by molding foamed particles in which the proportion of the position irregular unit is within the above range and using a polypropylene resin as the base resin for the core layer has a small compression set.

The above-mentioned position irregular unit based on 2,1-insertion and the position irregular unit based on 1,3-insertion both have the effect of lowering the crystallinity of the polypropylene resin containing these units in the structure. Have. More specifically, these position irregular units have the effect of lowering the melting point and the degree of crystallinity of the polypropylene resin.
These two actions show the effect of increasing the foamability when such a polypropylene resin is subjected to foaming, and the effect of reducing the compression set of the foam obtained. Therefore, the expanded particles using the above-described polypropylene resin having irregular units as the base resin for the core layer can be suitably used for foaming, and the expanded molded product obtained by molding the expanded particles is compressed. The permanent set is small.

  However, if the proportion of the position irregular units contained in the polypropylene resin is too high, the melting point and crystallization degree of the polypropylene resin are high, and the polypropylene resin is foamed as a base resin. In the case of the above, there is a possibility that the bubble diameter in the obtained foamed particles becomes coarse, the appearance of the molded body obtained from such foamed particles tends to be impaired, and the strength of the foamed molded body may be lowered. Is

Here, the fraction of structural units obtained from propylene in the polypropylene resin, the fraction of structural units obtained from ethylene and / or an α-olefin having 4 to 20 carbon atoms, and the isotactic triad fraction described later. The rate is a value measured using a ¹³ C-NMR method.
The measuring method of a ¹³ C-NMR spectrum is, for example, measured as follows.
That is, a sample of about 350 to 500 mg was taken in an NMR sample tube having a diameter of 10 mm, and completely dissolved using about 2.0 ml of o-dichlorobenzene as a solvent and about 0.5 ml of deuterated benzene for locking. Thereafter, measurement was performed at 130 ° C. under the complete proton decoupling condition.

As the measurement conditions, a flip angle of 65 deg and a pulse interval of 5T1 or more (where T1 is the longest value of the spin lattice relaxation time of the methyl group) were selected. In the polypropylene resin, since the spin lattice relaxation time of the methylene group and methine group is shorter than that of the methyl group, the recovery of the magnetization of all the carbons is 99% or more under these measurement conditions. In addition, although the detection of the position irregular unit by ¹³ C-NMR method is usually about 0.01%, the detection can be enhanced by increasing the number of integration.

For the chemical shift in the above measurement, the peak of the methyl group of the third unit of the 5-unit propylene unit that is head-to-tail bonded and has the same direction of methyl group branching is set as 21.8 ppm. The chemical shifts of other carbon peaks were set.
Using this criterion, the peak based on the methyl group of the second unit in the propylene unit 3 chain represented by PPP [mm] in the structural formula (Chemical Formula 1) shown below is 21.3 to 22.2 ppm. The peak based on the methyl group of the second unit in the three propylene unit chains represented by PPP [mr] is in the range of 20.5 to 21.3 ppm in the three propylene unit chain represented by PPP [rr]. The peak of the second unit based on the methyl group appears in the range of 19.7 to 20.5 ppm.

Here, PPP [mm], PPP [mr], and PPP [rr] are also represented by the following structural formulas.

The polypropylene resin containing a position irregular unit based on 2,1-insertion and 1,3-insertion of propylene contains a specific amount of partial structures (Ι) and (ΙΙ) of the following formula.

Such a partial structure is considered to be caused by positional irregularities that occur during polymerization when, for example, a polymerization reaction is performed using a metallocene polymerization catalyst.
That is, the propylene monomer usually reacts with a so-called “1,2-insertion” in which the methylene side is bonded to the metal component in the catalyst, but in rare cases, “2,1-insertion” or “1,3 -"Insert" may occur. “2,1-insertion” is a reaction mode in which the addition direction is opposite to “1,2-insertion”, and forms a structural unit represented by the above partial structure (構造) in the polymer chain.
Further, “1,3-insertion” means that propylene monomers C-1 and C-3 are incorporated into a polymer chain, and as a result, a linear structural unit, that is, the above partial structure (ΙΙ). Arise.

The polypropylene resin in which the proportion of each position irregular unit is in a specific range can be obtained by selecting an appropriate catalyst. Specifically, it can be obtained using, for example, a metallocene polymerization catalyst having a hydroazurenyl group as a ligand. Here, the metallocene polymerization catalyst comprises a transition metal compound component having a metallocene structure and a promoter component. The proportion of each position irregular unit varies depending on the chemical structure of the metal complex component of the catalyst used in the polymerization, but generally the higher the polymerization temperature, the higher the tendency. In the present invention, in order to bring the ratio of each position irregular unit of the polypropylene resin into a specific range, it is preferable to employ 0 to 80 ° C. as the polymerization temperature.

  The metal complex component can be used as a catalyst as it is, but it can also be used as a solid catalyst in which the metal complex component is supported on a particulate carrier that is an inorganic or organic granular or particulate solid. Good. When the metal complex component is supported on the fine particle carrier, the metal complex component is preferably 0.001 to 10 mmol, more preferably 0.001 to 5 mmol, per 1 g of the carrier.

  Among the metallocene polymerization catalysts having the hydroazurenyl group as a ligand, a catalyst using titanium, zirconium, or hafnium as a metal atom is preferable, and a complex containing zirconium is particularly preferable because of high polymerization activity.

  Among the metallocene polymerization catalysts, zirconium dichloride type complexes are preferably used, and among them, a cross-linked complex is particularly preferable. Specifically, for example, dimethylsilylene bis {1,1 ′-(2-methyl-4-phenyldihydroazulenyl)} zirconium dichloride and dimethylsilylene bis {1,1 ′-(2-ethyl-4-phenyldihydro). Azulenyl)} zirconium dichloride is preferably used. In this case, the proportion of each position irregular unit can be easily controlled, and a polypropylene resin having an isotactic triad fraction described later of 97% or more can be easily obtained.

  As co-catalyst components, aluminoxanes such as methylaluminoxane, isobutylaluminoxane, methylisobutylaluminoxane, Lewis acids such as triphenylborane, tris (pentafluorophenyl) borane, magnesium chloride, dimethylanilinium tetrakis (pentafluorophenyl) borate An ionic compound such as These promoter components can also be used in the presence of other organoaluminum compounds such as trialkylaluminum such as trimethylaluminum, triethylaluminum and triisobutylaluminum.

  The isotactic triad fraction in the entire polymer chain of the polypropylene resin is represented by the following formula. In the partial structure (ΙΙ), as a result of 1,3-insertion, only one methyl group derived from the propylene monomer has disappeared.

In this formula, ΣΙCH ₃ represents the area of all methyl groups (all peaks at 19-22 ppm of chemical shift). A <1>, A <2>, A <3>, A <4>, A <5>, A <6>, A <7>, A <8> and A <9> are respectively 42.3 ppm, 35.9 ppm, 38.6 ppm, 30.6 ppm, 36.0 ppm, 31.5 ppm, 31.0 ppm, 37.2 ppm, 27.4 ppm peak area, part in the above formula (Formula 2) The abundance ratio of carbon shown in the structures (Ι) and (ΙΙ) is shown.
The ratio of 2,1-inserted propylene and the ratio of 1,3-inserted propylene with respect to the total propylene insertion were calculated by the following formulas.

Further, in the present invention, the polypropylene resin, the melting point of the polypropylene resin when the Tm (° C.), the water vapor permeability in the case of molding the polypropylene resin film ^{Y (g / m 2 / 24hr} ), It is preferable that Tm and Y satisfy the following relational expression.

(Equation 3)
(−0.20) · Tm + 35 ≦ Y ≦ (−0.33) · Tm + 60

The water vapor permeability can be measured by JIS K7129 (1992) “Test method for water vapor permeability of plastic film and sheet”. In this measurement, an infrared sensor method is employed as a test method, and a test temperature of 40 ± 0.5 ° C. and a relative humidity of 90 ± 2% are employed as test conditions.
A polypropylene resin that satisfies the above formula exhibits moderate water vapor permeability. The moderate water vapor permeability promotes the penetration of the steam used for molding into the foamed particles (in the core layer) to improve the secondary foamability of the foamed particles, and there is no void between the foamed particles or Production of an extremely small foam-molded product is facilitated.

  Moreover, moderate water vapor permeability is a general method for producing foamed particles. After impregnating a foaming agent while dispersing resin particles in water, the foamed particles are released from high temperature and pressure to low pressure. In the method, the penetration of water and blowing agent into the resin particles is facilitated. As a result, water and the foaming agent are uniformly dispersed in the resin particles, the average cell diameter of the obtained foamed particles can be made uniform, and the expansion ratio can be improved.

The water vapor permeability (Y) is expressed in relation to the melting point (Tm) of the polypropylene resin. Generally, the foaming temperature during the production of the foamed particles and the steam temperature during the molding are determined by the base material. This is based on the fact that the higher the melting point (Tm) of the polypropylene resin, the higher the resin, and the lower the melting point (Tm).
By satisfying the relationship between the water vapor permeability (Y) and the melting point (Tm) of the polypropylene resin represented by the above formula, an appropriate steam or foaming agent permeation into the polypropylene resin forming the core layer is obtained. The average cell diameter of the foamed particles obtained is uniform, and finally it exhibits a sufficient compressive strength, resulting in an excellent foamed molded article having a small compression set.
In producing a polypropylene resin having a melting point (Tm) and water vapor permeability (Y) satisfying the above formula, it can be obtained by selecting an appropriate catalyst. Specifically, for example, it can be suitably obtained by using the above-mentioned metallocene polymerization catalyst, in particular, bridged bis {1,1 ′-(4-hydroazurenyl)} zirconium dichloride as a metal complex component.

Next, the polypropylene resin preferably further has an isotactic triad fraction (hereinafter referred to as “mm fraction”) measured by the ¹³ C-NMR method of 97% or more. The mm fraction is preferably 98% or more. When the mm fraction is 97% or more, the mechanical properties of the polypropylene resin become higher. By molding foamed particles having such a foam made of polypropylene resin as a core layer, it is possible to obtain a foamed molded article having further improved mechanical properties.

Next, the polypropylene resin forming the core layer preferably further has a melt flow rate of 0.5 g / 10 min to 100 g / 10 min. In this case, expanded particles can be produced while maintaining industrially advantageous production efficiency, and the mechanical properties of the expanded molded article can be improved.
When the melt flow rate (may be referred to as MFR) is less than 0.5 g / 10 minutes, the production efficiency of the expanded particles, particularly the productivity in the melt-kneading process described later, may be reduced. Moreover, when MFR exceeds said 100 g / 10min, there exists a possibility that mechanical physical properties, such as the compression strength of a foaming molding obtained by shape | molding foamed particle, and tensile strength, may become low. In addition, Preferably, MFR of polypropylene resin is 1.0-50 g / 10min, Furthermore, 1.0-30 g / 10min is good. The said MFR means the melt mass flow rate measured according to the conditions described in Table 3 of JIS K6921-2 (1997).

  The expanded particles used in the present invention can be usually obtained as follows. That is, it is usually obtained by foaming resin particles having a composite structure comprising a non-foamed core layer and a non-foamed coating layer.

Resin particles having such a composite structure are, for example, sheath-core type composites described in JP-B Nos. 41-16125, 43-23858, 44-29522, and JP-A-60-185816. Can be manufactured using a die.
In this case, two extruders are used, a polyolefin polymer that melts and kneads a crystalline polyolefin resin for forming a core layer in one extruder and forms a coating layer in the other extruder. After melt-kneading, each molten resin is introduced into a coextrusion die and laminated and merged to form a sheath-core type composite consisting of a non-foamed core layer and a non-foamed coating layer and pressed into a string shape. put out. Subsequently, the string-like material is cut into a predetermined weight or size with a cutting machine equipped with a take-up machine, and resin particles having a columnar or pellet-like composite structure composed of a non-foamed core layer and a coating layer are obtained. The method obtained is preferred.

  The thinner the coating layer of resin particles, the smaller the ratio of non-foamed portions when the composite resin particles are foamed, so that the expansion ratio can be increased. Coating becomes difficult. Further, if the thickness of the coating layer becomes too thick, bubbles are generated in the coating layer when the composite resin particles are foamed, the ratio of the non-foamed portion is substantially increased, and the mechanical strength of the obtained foamed molded product is increased. Will result in a decline. Therefore, the thickness of the coating layer is preferably 5 to 500 μm, more preferably 10 to 100 μm, with the resin particles before being produced into foamed particles. The thickness of the coating layer after production of the expanded particles is preferably 0.1 to 200 μm, and more preferably 0.5 to 60 μm. The coating layer in the expanded particles is substantially in an unexpanded state.

Here, “substantially non-foamed state” means not only when bubbles are not present at all (including the case where bubbles are once melted and destroyed but disappeared), as well as when fine bubbles are formed. It also means a slight presence. If there are a few minute bubbles, these bubbles may be those that do not communicate with each other, or those that break and communicate with each other. It is preferable that the maximum length of the bubbles observed with a microscope does not exceed 10 μm. When bubbles having a maximum length of 10 μm or less are present, the number of bubbles is preferably 3 or less and more preferably 2 or less per 500 μm ² of the cut surface of the coating layer.

  In addition, when extruding the above-described composite into a string shape, a foaming agent is contained in the polyolefin resin for core layer formation, and the sheath is formed of a foamed core layer and a substantially non-foamed coating layer. Although the core-type composite can be extruded and foamed in a string shape, the core layer-forming resin is usually extruded in a substantially non-foamed state. In general, the average weight of one resin particle is 0.1 to 20 mg. If the average weight of one resin particle is in the range of 0.2 to 10 mg and the variation in the weight between the particles is further small, the production of the expanded particles is facilitated, and the variation in the density of the obtained expanded particles is also reduced. .

  As a method of obtaining foamed particles from the resin particles, a method of impregnating the resin particles produced as described above with a physical foaming agent and then heat-foaming, specifically, for example, Japanese Patent Publication No. 49-2183 The methods described in JP-A No. 56-1344, West German Patent Publication No. 1285722 and No. 2107683 can be used.

  Examples of the physical foaming agent include aliphatic hydrocarbons such as butane, pentane, hexane, and heptane, halogenated hydrocarbons such as trichlorofluoromethane, dichlorodifluoromethane, tetrachlorodifluoroethane, and dichloromethane. Two or more kinds can be mixed and used. In addition, inorganic gases such as nitrogen, air, and carbon dioxide can also be used.

  When the resin particles are impregnated with a foaming agent and then heated and foamed, the resin particles are put together with a physical foaming agent and a dispersion medium in a pressure vessel that can be sealed and opened, and the softening temperature of the base resin of the core layer in the resin particles is exceeded. The resin particles are impregnated with a physical foaming agent. Thereafter, a method in which the content in the sealed container is discharged from the sealed container into a low-pressure atmosphere to foam the resin particles, and then a drying process is preferable for obtaining foamed particles.

It is preferable to use water, alcohol or the like as the dispersion medium. Furthermore, in order to uniformly disperse the resin particles in the dispersion medium, poorly water-soluble inorganic substances such as aluminum oxide, tricalcium phosphate, magnesium pyrophosphate, zinc oxide, and kaolin, and highly water-soluble substances such as polyvinyl pyrrolidone, polyvinyl alcohol, and methyl cellulose. It is preferable to use an anionic surfactant such as molecular protective colloid agent, sodium dodecylbenzenesulfonate, sodium alkanesulfonate, or a mixture of two or more.
Further, when releasing the resin particles in a lower pressure atmosphere than in the container, in order to facilitate the release, a pressure gas similar to that of the physical foaming agent is introduced into the sealed container to reduce the pressure in the sealed container. It is preferable to keep it constant.

  When obtaining a foamed particle having a foam made of crystalline polypropylene resin as a core layer by the above method, the foamed particle in which two or more melting peaks appear in the DSC curve obtained by calorimetry with the DSC apparatus described above is The secondary foamability is excellent, and the resulting foamed molded article has excellent mechanical strength and appearance. Such foamed particles are, for example, described in JP-A-2002-200355, etc., under conditions for foaming resin particles, specifically, holding temperature, holding time, and low-pressure atmosphere in a pressure vessel. It can be obtained by controlling the temperature, pressure, time, etc. during release.

Next, the manufacturing method of the foaming molding of this invention is demonstrated.
The method for producing a foamed molded article of the present invention continuously moves along the upper and lower surfaces in a passage having a rectangular cross section formed surrounded by a structural material including a thickness control member and a width control member. Manufactured using a molding apparatus that includes an endless belt, supplies foamed particles between the endless belts, and sequentially passes the supplied foamed particles through a heating region and a cooling region to continuously produce a foamed molded article. .

  That is, the foamed molded article of the present invention includes a foamed core layer made of a crystalline polyolefin resin, and a polyolefin having a melting point of 15 ° C. lower than the melting point of the polyolefin resin forming the core layer or a core layer. Expanded particles having a composite structure composed of a substantially non-foamed coating layer made of a polyolefin-based polymer having a Vicat softening point of 15 ° C. or more lower than the Vicat softening point of the resin, from the hopper to the structural material A steam supply chamber configured by supplying a pair of upper and lower steam particles is supplied between upper and lower endless belts that continuously move along the upper and lower surfaces in a passage having a rectangular cross-section. The foamed particles are secondary-foamed by passing through the heating zone provided to fuse the foamed particles together, and then passed through the cooling zone to continuously expand the plate-shaped polyolefin resin. To produce the form.

In addition, after a foaming part supplied from a hopper is compressed by providing a projecting portion in a passage from the foaming particle supply part of the molding apparatus to the molding part, a part of the compression can be released and then subjected to heat molding. When compressing foamed particles, it is preferable to compress until it becomes a bulk volume of 10-60% of the original bulk volume, and it is preferable to compress until it becomes a bulk volume of 15-50% especially. Further, when a part of the compression is released, a compression recovery rate of 80% or more, particularly 85% or more is preferable. By compressing and supplying the foamed particles in this way, it is possible to prevent the backflow of the foamed particles and the backflow of the crotch heating steam to the hopper side.
As a method for compressing the foamed particles, for example, projecting portions 17 and 17 as shown in FIG. 1 are provided on the upstream side of the heating region of the passage from the foamed particle supply unit to the molding unit and compressed by the projecting portions. Can do.

  The compression recovery rate of the expanded particles can be obtained from the following formula.

(Equation 4)
Compression recovery rate (%) = V ₂ / V ₁ × 100
(Where V ₁ is the original bulk volume of the expanded particles, and V ₂ is the bulk volume of the expanded particles 10 seconds after the compression of the expanded particles to 60% of the original bulk volume and then removing the compression. )

For example, a molding apparatus as shown in FIG. 1 is preferably used in the above manufacturing method.
FIG. 1 shows an example of a molding apparatus for producing the foamed molded article of the present invention. In the figure, 1 is a hopper that stores expanded particles, 2 is an upper belt that travels endlessly between the rolls 3a and 3b, and 4 is a lower belt that travels endlessly between the rolls 5a and 5b.

  The molding apparatus has a substantially cross-section surrounded by a structural material including thickness control members 7 and 8 and width control members (not shown) provided on both sides of the thickness control members 7 and 8. Foamed particles 6 are supplied between the upper and lower belts 2 and 4 that travel endlessly along the upper and lower surfaces of the passage 9 having a rectangular space, and the supplied foamed particles are the upper and lower belts 2 that travel endlessly. 4, the foamed particles are fused with each other by steam supplied from the chambers in a heating region composed of a pair of upper and lower chambers 11, 12, 13, 14, 15, and then a molded body 10 is obtained through a cooling region 16. It is configured to be Further, for example, the protrusions 17 and 17 as shown in FIG. 1 can be provided on the upstream side of the heating region of the passage from the expanded particle supply unit to the molding unit.

  In order to supply steam into the passage 9, the belts 2, 4 and the thickness control members 7, 8 need to have steam permeability. Usually, the belts 2 and 4 are stainless steel belts having a thickness of about 0.2 to 1.0 mm, and the belt has many through holes with a diameter of 0.5 to 3.0 mm at a pitch of about 3 to 50 mm. The thickness control members 7 and 8 are also provided with through holes of an appropriate size. Moreover, the steam in a channel | path can also be attracted | sucked through said through-hole as needed.

  In the illustrated apparatus, in the pair of upper and lower chambers provided along the passage 9, the chamber on the upstream side of the passage functions as a first heating region and the chamber on the downstream side functions as a second heating region. In the molding apparatus shown in the figure, the steam may be supplied from either side of the chambers disposed above and below the passage 9, and at least one chamber is a steam supply chamber, and the other chamber corresponding to the steam supply side chamber. Can function as a steam suction chamber if necessary.

For example, in the molding apparatus shown in the figure, when the chambers 12 and 13 are the first heating region and the chambers 14 and 15 are the second heating region, the chamber 12 disposed above the passage 9 in the first heating region, When supplying steam from 13, the corresponding chambers 12 and 13 arranged below the passage 9 can be connected to a suction line to form a suction chamber. The supply and suction of steam in the second heating zone of the chambers 14, 15 is similar to the first heating zone, with the steam supply corresponding to the chamber located above the passage and the suction corresponding to the bottom located in the passage. Done in the chamber. Further, the steam supply direction and suction in the second heating region may be performed from the direction opposite to the supply and suction in the first heating region.
As described above, in the first heating region and the second heating region, the supply direction of the forming steam may be performed from the same direction in both the first heating region and the second heating region. The forming steam may be supplied from the opposite direction. Further, when a plurality of chambers are arranged in the first heating region and the second heating region, respectively, supply and suction of the forming steam can be alternately performed in each heating region.
In addition, it is preferable that both the upper side and the lower side of all the chambers 11 to 15 are configured so as to be freely connectable to the forming steam supply line and the suction line by switching valves or the like.

  The molding apparatus may be provided with at least two sets of chambers so that the first heating area and the second heating area can be configured. However, as described above, it is necessary when the apparatus is provided with five sets of chambers. Depending on the case, suction can be performed on the upstream side of the first heating region, or on the downstream side of the second heating region, or in some cases, the foamed particles can be preheated in the chamber on the upstream side of the first heating region, Since the manufacturing efficiency of a molded object can be improved more, it is preferable.

  When the steam in the passage 9 is sucked on the upstream side (foamed particle supply side) of the first heating region, it is preferable because the foamed particles 6 are stably supplied into the passage 9, and the air between the foamed particles is exhausted. Therefore, it becomes easy to produce a foamed molded article having excellent fusion properties between the foamed particles. For example, when the steam is supplied by the chambers 12 and 13 as described above, the suction can be performed in the chamber 11 on the upstream side of the first heating region. Further, if necessary, suction may be performed in the chamber 14 on the downstream side of the second heating region. If suction is performed on the downstream side of the second heating region, the line speed can be further increased.

  In this case, in the pair of chambers 12 and 13, if either the upper or lower of the pair of chambers is used for supplying steam and the other chamber is used for sucking the steam in the passage 9, the foamed particles are efficiently heated. Molding with lower pressure steam becomes possible. As another heating method, if the upper side of the chamber 12 is supplied with forming steam, the chamber 12 opposite to the steam supply side is used for suction, and the chambers 13 and 13 are used as forming steam supply chambers, Compared with the heating method in which steam is alternately supplied to the upper side and the lower side, the supply amount of steam can be reduced.

When the polyolefin polymer forming the coating layer has a clear melting point, the temperature of the molding steam supplied in the first heating region and the second heating region is the internal pressure applied to the expanded particles and the bulk density of the expanded particles. Although slightly different depending on the size, based on the melting point of the polyolefin resin forming the core layer of the expanded particles (MPc (° C.)) and the melting point of the polyolefin polymer forming the coating layer (MPs (° C.)), MPs or more, Less than MPc is preferable.
If the temperature of the forming steam is too low, the fusion between the foamed particles is deteriorated. On the other hand, if the temperature is too high, the cooling time must be extended, which is not preferable. Therefore, the temperature of the forming steam is preferably [MPs + 1 ° C.] or more and [MPc-1 ° C.] or less, more preferably [MPs + 3 ° C.] or more and [MPc-3 ° C.] or less.

  Further, when the polyolefin polymer forming the coating layer does not show a clear melting point, the temperature of the molding steam supplied in the first heating region and the second heating region is the internal pressure applied to the expanded particles or the expanded particles. Although slightly different depending on the bulk density, the melting point (MPc (° C.)) of the polyolefin resin that forms the core layer of the expanded particles and the Vicat softening point (VSPs (° C.)) of the polyolefin polymer that forms the coating layer are the standards. As above, [VSPs + 10 ° C.] or more and less than MPc (° C.) is preferable, [VSPs + 15 ° C.] or more and [MPc-1 ° C.] or less is more preferable, and [VSPs + 20 ° C.] or more and [MPc−3 ° C.] or less is more preferable.

  The foamed molded article obtained as described above may start shrinking immediately after release depending on the type and apparent density of the crystalline polyolefin resin forming the core layer. By starting curing under an atmosphere of about 50 to 85 ° C. at an early stage, the dimensions can be recovered to substantially the same size as the space in the cooling zone.

  The expanded particles used in the production method of the present invention generally have a bulk density in the range of 8 g / L to 450 g / L, preferably in the range of 10 g / L to 300 g / L, and 12 g / L. The thing of the range of L-30g / L is more preferable. The bulk density of the foamed particles was randomly extracted from the foamed particles immediately before molding, and deposited naturally in a 1 L graduated cylinder in a 1 L graduated cylinder in an atmospheric pressure environment with a temperature of 23 ° C. and a relative humidity of 50%. A large number of expanded particles can be accommodated to a scale of 1 L so as to be in a state, and then the weight of the accommodated expanded particles can be measured.

The internal pressure applied to the expanded particles is preferably 0.03 to 0.35 MPa (G). By using foamed particles having an internal pressure of 0.03 to 0.35 MPa (G) as the foamed particles, foam molding with a small gap between particles having a desired foaming ratio and good fusion between the particles. The body is obtained and the cooling efficiency is high. When the internal pressure is low, it is difficult to obtain a foamed molded product having a small gap between the particles unless the foamed particles are compressed and molded.
When foamed particles are compressed and molded, a foamed molded product having a large expansion ratio cannot be obtained.
On the other hand, when the internal pressure of the particles is too high, the cooling efficiency in the cooling zone of the molding apparatus is lowered, and in order to prevent abnormal expansion of the foamed molded product, a considerably long time is required for cooling, and the effect of the present invention May become smaller.

Expanded particles to which internal pressure is applied are placed in an airtight container and left for an appropriate time with pressurized air supplied to the container, such as air so that the pressure inside the expanded particles exceeds atmospheric pressure. Obtained by impregnating the expanded gas into the expanded particles.
The gas for pressurization can be used without any problem as long as the main component is an inorganic gas that does not liquefy or solidify under the required pressure, but one or more inorganic gases selected from nitrogen, oxygen, air, carbon dioxide, and argon In particular, nitrogen and air are preferable in consideration of environmental load and cost.

The internal pressure P (MPa (G)) of the expanded particles whose internal pressure has been increased can be determined, for example, by the method described in JP-A-2003-201361.
First, the foamed particles used for molding are placed in a closed container, and pressurized air is maintained in the container, and the air pressure in the container is normally maintained in the range of 0.98 to 9.8 MPa (G) as a gauge pressure. As described above, the internal pressure can be increased by allowing the air to permeate into the expanded particles by leaving the supplied state for an appropriate time. The expanded particles whose internal pressure has been sufficiently increased are supplied to the hopper 1 of the molding apparatus. The measurement of the internal pressure of the expanded particles is obtained by performing the following operation using a part of the expanded particles in the hopper 1 immediately before molding (hereinafter referred to as expanded particle group).

  An appropriate amount of foamed particles with an increased internal pressure are taken from a pressurized tank into a polyethylene bag of about 70 mm × 100 mm having a large number of fine holes through which the foamed particles cannot pass but air can pass freely. The weight is measured in a constant temperature room at 50 ° C. and a relative humidity of 50% under atmospheric pressure. Let this weight be Q (g). The weight after standing for 48 hours in the same temperature chamber is measured, and this weight is defined as U (g). Next, the foamed particles are taken out and the weight of the bag is measured. Let the weight be Z (g). The difference between Q (g) and U (g) is defined as the increased air amount W (g), and the internal pressure P (MPa (G)) of the expanded particles is calculated by the following formula.

(Equation 5)
P = (W ÷ M) × R × T ÷ V
However, in the above formula, M is the molecular weight of air, R is the gas constant, T is the absolute temperature (K), V is the volume obtained by subtracting the volume of the base resin in the foamed particles from the apparent volume of the foamed particles (L). It is.
The apparent volume (L) of the expanded particles is determined by submerging the entire amount of expanded particles taken out of the bag after 48 hours into water in a measuring cylinder containing 100 cm ^{3 of} 23 ° C. water in the same constant temperature room. From the scale, the volume Y (cm ³ ) of the expanded particle group is calculated, and this is calculated by converting the unit into liters (L). The apparent expansion ratio of the expanded particles can be obtained by dividing the density (g / cm ³ ) of the base resin by the apparent density (g / cm ³ ) of the expanded particles. The apparent density (g / cm ³ ) of the expanded particles can be obtained by dividing the weight of the expanded particles (difference between U (g) and Z (g)) by the volume Y (cm ³ ).
In the above measurement, a plurality of foams in such an amount that the weight of foamed particles (difference between U (g) and Z (g)) is 0.5000 to 10.0000 g and the volume Y is 50 to 90 cm ^3. Particle groups are used.

  The apparent density of the foam molded product obtained by the method for producing a foam molded product of the present invention is generally in the range of 10 g / L to 450 g / L. The thing of the range of 10 g / L-300 g / L is preferable, and the thing of the range of 10 g / L-28 g / L is more preferable. Moreover, although the thickness of 1-20 cm and width 10-150 cm are common, the foaming molding obtained is preferable that thickness is 3-10 cm and width is 20-100 cm. A foamed molded article having an apparent density of 10 g / L to 28 g / L is suitable as a buffer packaging material or the like.

  The apparent density of the foamed molded product means the apparent overall density defined by JIS K7222 (1999).

Next, examples of the present invention will be described.
In this embodiment, expanded particles having a composite structure comprising a foamed core layer made of a polypropylene resin as a base resin and a coating layer made of a polyethylene polymer, and the molding apparatus shown in FIG. Is used to produce a foam molded article.

[Manufacture of polypropylene resin]
First, a polypropylene resin as a base resin for forming a core layer is prepared by the following production examples 1 and 2.
It was synthesized by the method shown in

Production Example 1
(I) Synthesis of dimethylsilylenebis {1,1 ′-(2-methyl-4-phenyl-4-hydroazurenyl)} zirconium dichloride All the following reactions are carried out in an inert gas atmosphere, and the reaction is preliminarily dried and purified. The solvent used was used.

(A) Synthesis of racemic / meso mixture 2.22 g of 2-methylazulene synthesized according to the method described in JP-A-62-207232 was dissolved in 30 mL of hexane, and 15.6 mL of cyclohexane-diethyl ether solution of phenyllithium ( 1.0 equivalent) was added in small portions at 0 ° C.
The solution was stirred at room temperature for 1 hour, cooled to -78 ° C, and tetrahydrofuran (30 mL).
Was added.
Next, 0.95 mL of dimethyldichlorosilane was added to this solution, and then the temperature was raised to room temperature and further heated at 50 ° C. for 90 minutes. Thereafter, a saturated aqueous solution of ammonium chloride was added, the organic layer was separated and dried over sodium sulfate, and the solvent was distilled off under reduced pressure.
The resulting crude product was purified by silica gel column chromatography (hexane-: dichloromethane = 5: 1) to give bis {1,1 ′-(2-methyl-4-phenyl-1).
, 4-dihydroazulenyl)} dimethylsilane 1.48 g.
786 mg of the bis {1,1 ′-(2-methyl-4-phenyl-1,4-dihydroazulenyl)} dimethylsilane obtained above was dissolved in 15 mL of diethyl ether, and this solution was dissolved in −78 ° C. at −78 ° C. -1.98 mL of butyllithium in hexane (1.68 mol / L) was added dropwise, the temperature was gradually raised to room temperature, and then the mixture was stirred at room temperature for 12 hours. The solid obtained by distilling off the solvent under reduced pressure was washed with hexane and dried under reduced pressure.
Furthermore, 20 mL of a toluene-diethyl ether mixed solvent (40: 1) was added, 325 mg of zirconium tetrachloride was added at −60 ° C., the temperature was gradually raised, and the mixture was stirred at room temperature for 15 minutes.
The obtained solution was concentrated under reduced pressure, and reprecipitated by adding hexane, thereby forming a racemic product composed of dimethylsilylene bis {1,1 ′-(2-methyl-4-phenyl-4-hydroazurenyl)} zirconium dichloride. A 150 mg / meso mixture was obtained.

(B) Separation of racemic body 887 mg of a racemic / meso mixture obtained by repeating the above reaction was put in a glass container, dissolved in 30 mL of dichloromethane, and irradiated with a high pressure mercury lamp for 30 minutes. Thereafter, dichloromethane was distilled off under reduced pressure to obtain a yellow solid.
To this solid, 7 mL of toluene was added, stirred, and allowed to stand to precipitate a yellow solid. The supernatant was removed, and the solid was dried under reduced pressure to obtain 437 mg of a racemate consisting of dimethylsilylene bis {1,1 ′-(2-methyl-4-phenyl-4-hydroazurenyl)} zirconium dichloride.

(Ii) Synthesis of metallocene polymerization catalyst (a) Treatment of catalyst carrier 135 mL of demineralized water and 16 g of magnesium sulfate were placed in a glass container and mixed to obtain a solution. After adding 22.2 g of montmorillonite (“Kunipia-F” manufactured by Kunimine Kogyo Co., Ltd.) to this solution, the temperature was raised and kept at 80 ° C. for 1 hour.
Subsequently, after adding 300 mL of demineralized water, it filtered and isolate | separated solid content. After adding 46 mL of demineralized water, 23.4 g of sulfuric acid, and 29.2 g of magnesium sulfate to this solid content, the temperature was raised and the mixture was treated with heating under reflux for 2 hours, and then 200 mL of demineralized water was added and filtered.
Further, 400 mL of demineralized water was added and filtration was performed twice. Thereafter, the solid was dried at 100 ° C. to obtain chemically treated montmorillonite as a catalyst carrier.

(B) Preparation of catalyst component After the inside of a stirred autoclave having an internal volume of 1 liter was sufficiently substituted with propylene, 230 mL of dehydrated heptane was introduced, and the temperature inside the autoclave was maintained at 40 ° C.
Here, 10 g of chemically treated montmorillonite was suspended in 200 mL of toluene and added as the catalyst carrier prepared above.
Furthermore, the racemic form (0.15 mmol) of dimethylsilylenebis {1,1 ′-(2-methyl-4-phenyl-4-hydroazurenyl)} zirconium dichloride prepared in a separate container in (b) of (i) above. ) And triisobutylaluminum (3 mmol) in toluene (total 20 mL) were added to the autoclave.
Thereafter, propylene was introduced at a rate of 10 g / hr for 120 minutes, and then the polymerization reaction was continued for 120 minutes. Thereafter, the solvent was distilled off under a nitrogen atmosphere and dried to obtain a solid catalyst component. This catalyst component contained 1.9 g of polymer per 1 g of the solid component.
The solid catalyst component is a chemically treated montmorillonite, a racemic dimethylsilylene bis {1,1 ′-(2-methyl-4-phenyl-4-hydroazurenyl)} zirconium dichloride supported thereon, and triisobutyl. Composed of aluminum.

(Iii) Polymerization of polypropylene-based resin After the inside of a 200 L stirred autoclave is sufficiently substituted with propylene, 60 L of purified n-heptane is introduced, and 500 mL (0.12 mol) of hexane solution of triisobutylaluminum is added. The temperature inside the autoclave was raised to 70 ° C. Thereafter, the solid catalyst component (9.0 g) is added, and a mixed gas of propylene and ethylene (propylene: ethylene = 97.5: 2.5 (weight ratio)) is set to a pressure of 0.7 MPa (G). To initiate polymerization, and a polymerization reaction was carried out at 70 ° C. for 3 hours under the same pressure.
Thereafter, 100 mL of ethanol was injected into the reaction system to stop the reaction, and the residual gas component was purged to obtain 9.3 kg of polymer. This polymer has MFR = 8 g / 10 min, structural unit obtained from propylene is 97.6 mol%, structural unit obtained from ethylene is 2.4 mol%, and isotactic triad fraction is 99.2%. The melting point (Tm) was 141 ° C., the ratio of position irregular units based on 2,1-insertion was 1.06%, and the ratio of position irregular units based on 1,3-insertion was 0.17%.
Hereinafter, the propylene resin (propylene / ethylene random copolymer) obtained here is referred to as “polymer 1”.

Production Example 2
After thoroughly replacing the inside of the stirred autoclave with an internal volume of 200 L with propylene, 60 L of purified n-heptane is introduced, 500 mL (0.12 mol) of hexane solution of triisobutylaluminum is added, and the inside of the autoclave is raised to 70 ° C. Warm up. Thereafter, the same solid catalyst component (6.0 g) as in Production Example 1 was added, and a mixed gas of propylene and ethylene (propylene: ethylene = 96.5: 3.5 (weight ratio)) was applied at a pressure of 0.7 MPa (G ) To initiate polymerization, and the polymerization reaction was carried out at 70 ° C. for 3 hours under the same pressure.
Thereafter, 100 mL of ethanol was injected into the reaction system to stop the reaction, and the remaining gas component was purged to obtain 8.8 kg of a polymer as a propylene polymer for the core layer.
This polymer is obtained from ethylene with MFR = 8 g / 10 min, isotactic triad fraction of 99.2%, melting point (Tm) of 125 ° C., structural unit obtained from propylene, 95.3 mol%. The structural unit was 4.7 mol%, the ratio of the position irregular unit based on 2,1-insertion was 0.95%, and the ratio of the position irregular unit based on 1,3-insertion was 0.11%. .
Hereinafter, the polypropylene resin (propylene / ethylene random copolymer) obtained here is referred to as “polymer 2”.

[Polypropylene resin using Ziegler catalyst]
As a polypropylene resin using a Ziegler catalyst, “Novatech PP MB3B” (hereinafter referred to as “Polymer 3”) which is a propylene-butene-1 random copolymer manufactured by Nippon Polychem Co., Ltd. and Idemitsu Kosan Co., Ltd. A trade name “J532MZV” (hereinafter referred to as polymer 4), which is a propylene-ethylene random copolymer, was prepared.
Table 1 shows the physical properties of Polymer 1 to Polymer 4.

Next, production examples of foamed particles using the above polymers 1 to 4 and production examples of foamed molded products using these foamed particles will be described.
In the following examples, each physical property was obtained as follows.
Melting point: Measured by the above-mentioned method using a heat flux differential scanning calorimeter (DSC) “DSC-50” manufactured by Shimadzu Corporation.
Water vapor permeability: A film having a thickness of 25 microns was prepared from the polymers 1 to 4 and measured by the method described above.

Example 1
Using a 65 mm caliber single screw extruder, 100 parts by weight of the polypropylene resin (Polymer 1) obtained in Production Example 1 and 0.05 parts by weight of an antioxidant (trade name “Yoshinox BHT” manufactured by Yoshitomi Pharmaceutical Co., Ltd.) A specialty chemical company product name “Irganox 1010” (0.10 parts by weight) was added and kneaded at 230 ° C., and a core introduction nozzle for a reversing die having a sheath core structure so that an extrusion amount of 46 kg / hr was obtained. The molten resin was injected at a pressure of 14.7 MP (G).
Further, linear low density polyethylene polymerized using a metallocene polymerization catalyst having a density of 0.907 g / cm ³ and a melting point of 100 ° C. using a 30 mm caliber single screw extruder (trade name, manufactured by Nippon Polychem Co., Ltd.) "Kernel KF270") 100 parts by weight of antioxidant (trade name "Yoshinox BHT" manufactured by Yoshitomi Pharmaceutical Co., Ltd. 0.05 parts by weight, and product name "Irganox 1010" 0.10 parts by weight manufactured by Ciba Specialty Chemicals) The molten resin was injected at a pressure of 12.7 MPa (G) into the sheath introduction nozzle of a combination die having a sheath core structure so that the extrusion amount was 8 kg / hr.
Next, from the die orifice having a diameter of 1.5 mm, the kneaded product of the polymer 1 and the antioxidant is used as a non-foamed core layer, and the linear low-density polyethylene is used as a non-foamed coating layer. Extruded into a strand.
The strand was cooled through a water bath and cut so that the weight of one strand was 1.0 mg, to obtain resin particles having a composite structure. When the resin particles are observed with a phase contrast microscope, the coating layer made of linear low-density polyethylene having a thickness of 47 microns has a structure in which a non-foamed core layer made of polypropylene resin is covered in a cylindrical shape. It was.

Next, in order to make the resin particles into expanded particles, 1000 g of resin particles are mixed with 2500 g of water, 200 g of tribasic calcium phosphate (however, 10% aqueous dispersion) and 30.0 g of sodium dodecylbenzenesulfonate (2% aqueous solution). The product was placed in a 5 liter autoclave, and further the amount of isobutane shown in Table 2 was added. The temperature was raised to the foaming temperature shown in Table 2 over 60 minutes, and then kept at this temperature for 30 minutes.
Thereafter, in order to maintain the pressure in the autoclave at the foaming pressure shown in Table 2, while adding compressed nitrogen gas from the outside, the valve at the bottom of the autoclave was opened to release the contents to the atmosphere.
After the foamed particles obtained by the above operation were dried, the bulk density was measured and found to be 18 g / L. Further, the bubbles of the expanded particles were very uniform with an average cell diameter of 190 μm.
In addition, the average cell diameter of the expanded particles is a micrograph obtained by observing a section of the expanded particles cut through a substantially selected center of the expanded particles with a microscope, or this section with a microscope. In the micrograph obtained by observing, or the cross-section projected on the screen, the maximum diameter of each bubble was measured for 50 random bubbles, and the average value was shown.

Next, using the above-mentioned expanded particles, a foamed molded product was produced as follows.
First, the foamed particles obtained above are accommodated in pressurized air at 23 ° C. and a gauge pressure of 2 MPa, and the foamed particles are impregnated with air to increase the internal pressure of the foamed particles. Next, the foamed particles with the increased internal pressure were subjected to molding at the internal pressure shown in Table 2.

  Using an apparatus similar to the molding apparatus shown in FIG. 1, the expanded particles supplied from the hopper are made to have the original bulk volume by the protrusions 17 provided in the passage from the expanded particle supply section of the molding apparatus to the molded section. After compression to 40%, part of the compression was released to 80% of the original bulk volume, and then subjected to heat molding. The apparatus used here has a constant width of 30 cm in the passage 9 from the supply part of the expanded particles to the outlet of the molded body, and in the passage from the passage 17 having a width of 30 cm to the molded body outlet in the cooling region. Has a constant height of 5 cm. The length from the center of the roll 3b to the protrusion 17 is 1.5 m, the length of the protrusion 17 is 20 cm, the length from the end of the protrusion 17 to the cooling means 16 is 2 m, the length of the cooling means 16 The length is 6 m. The conditions such as supply of forming steam and suction in each chamber are shown in the column of chamber pressure in Table 2. In Table 2, the first to fifth chambers indicate the most upstream chamber 11 to the most downstream chamber 15 in order. Moreover, the value of the pressure in the chamber of Table 2 showed the pressure (MP (G)) of the supplied forming steam. “Vac.” Indicates that the inside of the chamber was sucked with a vacuum pump. “N” indicates that neither the supply of the forming steam nor the suction was performed. Table 2 shows the line speed at the time of molding and the properties of the obtained foamed molded article.

  As the pressure of the forming steam, the lowest pressure at which the fusion between the foamed particles becomes good is adopted, and the line speed of the formed body is always set to 60 ° C. for the foamed formed body immediately after production. Move to a curing room under pressure, let stand for 24 hours, then move to a room at 23 ° C. and atmospheric pressure, measure the widthwise dimension of the foamed molded product after 24 hours, and this dimension is the dimension of the outlet of the molding device. Adopted the speed when it was 99%.

Examples 2-4
It implemented like Example 1 except having used the above-mentioned polymer 2, polymer 3, and polymer 4 as base material resin which forms a core layer, and those results were shown in Table 2 as Examples 2-4.

Comparative Example 1
The same procedure as in Example 1 was performed except that the resin of the coating layer in Example 1 was changed to that shown in Table 3, and the results are shown in Table 3.

Comparative Examples 2-4
Polypropylene-based resin expanded particles having no coating layer were prepared as follows, and a foamed molded product was produced using the prepared polypropylene resin expanded particles.
First, polymer 1 (Comparative Example 2) or polymer 3 (Comparative Example 3 and Comparative Example 4) was kneaded using a single screw extruder having an inner diameter of 30 mm, and the weight of one resin particle was adjusted to 1.0 mg according to a conventional method. It cut so that it might become, and it was set as the resin particle.
Next, 1000 g of each resin particle was placed in an autoclave having an internal volume of 5 liters together with 3000 g of water, 200 g of tribasic calcium phosphate (however, 10% aqueous dispersion) and 25.0 g of sodium dodecylbenzenesulfonate (2% aqueous solution). Isobutane was added in the amount shown in Table 3 and the temperature was raised to the foaming temperature shown in Table 3 over 60 minutes, and then maintained at this temperature for 30 minutes.
Thereafter, in order to maintain the pressure in the autoclave at the foaming pressure shown in Table 3, while adding compressed nitrogen gas from the outside, the contents were discharged from the bottom of the autoclave to the atmosphere to obtain expanded particles. Table 3 shows the results of measuring the bulk density after drying the foamed particles obtained above.
Next, using these foamed particles, a foam-molded article was produced in the same manner as in Example 1. Further, this foamed molded product was evaluated in the same manner as in Example 1. The results are shown in Table 3.
As a reference example, data of Example 4 using an ethylene-propylene random copolymer as a polymer of JP-A No. 2000-15708 is also shown in Table 3 as a reference example.

The molding pressures shown in Tables 2 and 3 were expressed as molding temperatures as follows.
0.12 MPa (G) = 124 ° C., 0.15 MPa = 127 ° C., 0.06 MPa (G) = 113 ° C., 0.14 MPa = 126 ° C., 0.17 MPa (G) = 130 ° C., 0.2 MPa = 134 ° C. 0.25 MPa (G) = 139 ° C., 0.28 MPa = 142 ° C., 0.35 MPa (G) = 148 ° C.

  As shown in Table 2, in Examples 1 to 4 using the expanded particles having the composite structure of the present invention, any expansion molding does not occur in the obtained expanded molded article even when the line speed is increased. I understand. The foamed moldings obtained in Examples 1 to 4 were not cracked even if they were bent by 90 ° by hand with respect to the fusion property between the foamed particles. As for the appearance of the foamed molded product, there were few gaps between the foamed particles and the surface was smooth.

On the other hand, Comparative Example 1 is a foamed particle in which the difference between the melting point of the thermoplastic resin forming the core layer and the melting point of the polyolefin polymer forming the coating layer is less than 15 ° C. as the foamed particle. In order to fuse, it is necessary to employ a higher molding steam pressure than in the examples. As a result, in order to produce a good molded product, the line speed has to be reduced.
That is, when compared with Example 1, the upper second chamber pressure is 0.12 MPa (G), the upper third chamber pressure is 0.15 MPa (G), the lower third chamber pressure is 0.15 MPa, In contrast, Comparative Example 1 required 0.25 MPa (G). The line speed is 3.0 m / min. In Example 1. In contrast, in Comparative Example 1, 2.5 m / min. It is.

Comparative examples 2 and 3 are respectively contrasted with examples 1 and 3 and show examples using single-layer expanded particles having no coating layer. In Comparative Examples 2 and 3, in order to fuse the expanded particles, it is necessary to employ a high molding steam pressure. As a result, the line speed has to be reduced to produce a good molded product. .
Moreover, the comparative example 4 is contrasted with Example 3, and shows the example using the single layer expanded particle which does not have a coating layer. In Comparative Example 4, the obtained foamed molded article had poor fusion between the foamed particles and was easily broken by hand. Compared to Example 3, the appearance of Comparative Example 4 was large in the gaps between the foamed particles. The appearance was poor.
While the line speed of the reference example is 2.5 m / min, the line speeds of Examples 1 to 4 are values exceeding 2.5 m / min, indicating that the production efficiency is excellent.

An example of the shaping | molding apparatus which manufactures a foaming molding continuously in this invention is shown.

Explanation of symbols

1 ... hopper 2, 4 ... endless belts 3a, 3b, 5a, 5b that move continuously ... roll 6 ... expanded particles,
7, 8 ···· Regulating plate 9 ··· Cross passage 10 ··· Molded bodies 11, 12, 13, 14, 15 ··· Chamber 16 ··· Cooling means 17 ··· .... Protrusions

Claims (4)

  The polyolefin resin expanded particles supplied by supplying polyolefin resin expanded particles between endless belts that continuously move along the upper and lower surfaces in a passage having a rectangular shape surrounded by a structural material. In the method of continuously producing a foamed molded article by sequentially passing through a heating region and a cooling region, a foamed core layer made of a crystalline polyolefin resin and a core layer are formed as the polyolefin resin foam particles. A non-polyolefin polymer having a melting point of 15 ° C. or more lower than the melting point of the polyolefin resin, or a polyolefin polymer having a Vicat softening point of 15 ° C. or more lower than the Vicat softening point of the polyolefin resin forming the core layer. Polyolefin resin characterized by using expanded particles having a composite structure composed of a coating layer in an expanded state Continuous process of foam moldings.   The method for continuously producing a polyolefin-based resin foam molded article according to claim 1, wherein the foamed particles are foamed particles to which an internal pressure of 0.03 to 0.35 MPa (G) is applied.   The temperature of the forming steam supplied in the heating region is the melting point (MPc (° C.)) of the polyolefin resin forming the core layer of the expanded particles and the coating when the polyolefin polymer forming the coating layer exhibits a melting point. When the melting point (MPs (° C.)) of the polyolefin polymer forming the layer is used as a reference, the core layer of the foamed particles when the polyolefin polymer does not exhibit a clear melting point when the temperature is not lower than MPs and lower than MPc. Based on the melting point (MPc (° C.)) of the polyolefin resin forming the coating layer and the Vicat softening point (VSPs (° C.)) of the polyolefin polymer forming the coating layer, it should be not less than [VSPs + 10 ° C.] and less than MPc. The continuous manufacturing method of the polyolefin-type resin foam molding of Claim 1 or 2 characterized by the above-mentioned. The method for continuously producing a polyolefin resin foam molded article according to any one of claims 1 to 3, wherein the polyolefin polymer comprises a polyethylene polymer having a melting point of 125 ° C or lower.

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