JPH04110331A - Stretched hollow molding - Google Patents

Abstract

PURPOSE:To prepare the title molding excellent in strengths, rigidity, and pearly gloss by selecting the title molding having a specified apparent density and prepd. by stretching a compsn. comprising a specific high-density PE and a specific petroleum resin. CONSTITUTION:The title molding having an apparent density of 0.92g/cm<3> or lower and prepd. by stretching a compsn. comprising 100 pts.wt. high-density PE having a density of 0.94g/cm<3> or higher and 5-150 pts.wt. petroleum resin having a softening point (ring and ball method) of 160-220 deg.C (e.g. a hydrogenated cyclopentadiene petroleum resin) at least monoaxially is selected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a cavity-containing stretch-molded product and a method for producing the same. More specifically, the present invention relates to a cavity-containing stretched molded product in which a large number of fine voids are generated in the molded product, and a method for producing the same.

[Conventional technology]

Cavity-containing molded products are lightweight and have opacity, light-shielding properties, decorative properties, paper-like properties, etc.
- It is widely used in general packaging materials, decorative materials, calligraphy printing paper, etc. in the form of woven or biaxially stretched films or sheets, and in packaging materials, weaving threads, etc. in the form of tapes, ribbons, or filaments.

Conventionally, as a method for manufacturing a cavity-containing stretch molded product, (
1) A method of adding a foaming agent during molding to form a large number of bubbles, (2) Japanese Patent Publication No. 63-24532, Japanese Patent Application Laid-open No. 1983
A method is known in which a composition containing a large amount of an inorganic filler is stretched to form voids, as described in Japanese Patent No. 3-117043.

, However, these methods have the following drawbacks. In other words, regarding (1), it is necessary to select the blowing agent depending on the molding conditions and application, and the bubbles tend to become coarse and the gloss decreases, and in the case of thin films such as thin films, uniform fine foaming is difficult, and high-magnification stretching is difficult. The necessary biaxial stretching has the drawback that it is easy to stretch and break, making it difficult to produce a thin film. Regarding 2), is there an advantage that adding a large amount of inorganic filler causes many cavities during stretching? It causes poor dispersion, etc., and it takes a long time to replace the resin, and in the case of thin film stretching, the productivity is extremely poor, such as the quality of the product due to stretching breakage, and the resulting product has low gloss and is dull. However, it has the disadvantage that impact resistance, tensile strength, etc. are also low.

[Problem to be solved by the invention]

The purpose of the present invention is to eliminate the drawbacks of the conventional methods and to provide a hollow-containing stretched molded product in which uniform and fine voids are formed, which is difficult to obtain with inorganic filling and high percentage addition systems, and a method for stretching the molded product with high productivity. It is to provide.

[Means to solve the problem]

The present inventors conducted intensive research to solve the above problems, and found that by stretching a composition containing a specific amount of high-density polyethylene and a specific high softening point petroleum resin under specific conditions, Countless fine voids occur in the molded product,
The present invention was completed based on the discovery that a lightweight hollow-containing stretch molded product that is opaque, has excellent surface gloss, and is lightweight can be obtained.

The cavity-containing stretched molded product of the present invention is prepared by blending 5 to 150 parts by weight of a high softening point petroleum resin with a softening point (ring and ball method) of 160 to 220°C to 100 parts by weight of high-density polyethylene having a density of 0.94 or more. It is characterized in that it is made by stretching a composition of various sizes in at least one direction, and has an apparent density of 0.92 or less.

In addition, in the method for producing a cavity-containing stretch molded product of the present invention, 5 to 50 parts of high softening point petroleum resin having a softening point (ring and ball method) of 160 to 220°C is added to 100 parts by weight of high-density polyethylene having a density of 0.94 or more. 150 parts by weight of the composition is formed into an unstretched original fabric by a melt extrusion method, and then stretched at least twice in one direction at a temperature below the crystal melting point of the high-density polyethylene. Features.

In the above molded product and manufacturing method, the high softening point petroleum resin is a cyclopentadiene petroleum resin, a hydride of a cyclopentadiene petroleum resin, or a mixture of a cyclopentadiene petroleum resin and its hydride, and is a cyclopentadiene component. or contains 70% or more of a cyclopentadiene component and has a softening point of 170
A hydride of a cyclopentadiene petroleum resin having a temperature of ~200°C, a UV absorbance of 0.8 or less, and an iodine value of 30 or less can be used.

The high-density polyethylene used in the molded articles and production methods of the present invention can be prepared alone or in combination with ethylene in the presence of coordination or organometallic catalysts such as so-called Ziegler catalysts, 7-transition metal oxide catalysts or similar catalysts. small amounts of propylene, butene-1, pentene-1,4-methyl-
Among polymers, copolymers, or mixtures thereof obtained by polymerizing α-olefins such as pentene-1 and octene-1 under medium or low pressure, the density thereof is 0.94 or more. It is known that this high-density polyethylene is characterized by exhibiting a high degree of crystallinity with a crystallinity of 60% or more as measured by X-ray diffraction.

Among these, the density is in the range of 0.945 to 0.970,
And test condition 4 of JIS K7210-1976 (
190°C, 2.16 kgf) The melt flow rate (hereinafter referred to as MFR) determined by API is 0.3 to 3.
A value in the range of 0 is preferred.゛The higher the cyclopentadiene component in the high softening point petroleum resin used in the molded product and manufacturing method of the present invention, the better the opacification and weight reduction effects aimed at in the present invention. It is necessary and preferably contains 70% by weight or more, particularly preferably 90% by weight or more.

Moreover, it is limited to those having a softening point (ring and ball method) of 160 to 220°C. Those with a softening point (ring and ball method) of less than 160°C can form cavities in stretched products, and conversely, similar to alicyclic saturated hydrocarbon resins shown in JP-A-2-160532, etc. It acts in the direction of making the stretched polyethylene product transparent and does not form cavities in the molded product. Especially the softening point (
Conventional hydrogenated petroleum resins whose temperature (ring and ball method) is 140° C. or lower are conventionally used to make stretched polyethylene products transparent, and cannot be applied to the molding method and manufacturing method of the present invention. In addition, those having a softening point (ring and ball method) exceeding 220°C are undesirable because the compatibility with polyethylene is significantly reduced and the molded product becomes non-uniform.

The cavity molding of the molded product according to the present invention has the unique effect of using a high softening point resin (ring and ball method) of 160°C or higher. Since the solubility is good and the compatibility is very good during the unstretched stage, countless extremely fine voids are generated in the drawn product, resulting in a void-containing stretched product that is opaque and has a pearl-like luster. obtained and particularly preferred.

As the hydride of the cyclopentadiene petroleum resin, those having a softening point (ring and ball method) of 170 to 220°C, a UV absorbance of 0.8 or less, and an iodine value of 30 or less are particularly preferred. Note that a mixture with a low apparent softening point may be obtained by mixing low softening point substances with a softening point of less than 160°C, but in this case, the blending amount of components with a softening point of 160°C or higher is within the scope of the present invention. It is necessary that the

The molded article and the composition used in the manufacturing method of the present invention are obtained by distributing 5 to 150 parts by weight of a high softening point petroleum resin to 100 parts by weight of high-density polyethylene. If the blending amount of the resin is less than 5 parts by weight, cavity formation in the molded product of the present invention is insufficient, and the molded product cannot be made lightweight or opaque. 15
If the amount exceeds 0 parts by weight, extrusion unevenness and stretch breakage will become severe during molding, making molding substantially difficult. To obtain a cavity-containing stretch molded product with excellent productivity and stability over a wide molding range,
The hydride of the cyclopentadiene resin is preferably blended in an amount of 7 to 120 parts by weight, more preferably 10 to 100 parts by weight, per 100 parts by weight of high-density polyethylene.

Various additives, polymers, and the like that are known to be added to polyethylene resins may also be incorporated into the above-mentioned composition, as necessary, to the extent that they do not impair the purpose of the present invention. For example, additives include processing stabilizers, antioxidants, lubricants, slip agents, antistatic agents, etc.; polymers include ethylene polymers such as low-density polyethylene, linear low-density polyethylene, and linear low-density polyethylene; Examples include plastic elastomers and various polymers.

This composition can be easily prepared by blending it with an ordinary blender or mixer, but it is preferable to melt and mix it using an extruder, Banbury mixer, etc. and use it as a pellet-like composition. Particularly preferred. Also, for high density polyethylene or other resins,
It is also useful to add a large amount of the resin, make it into multiple batches, and then blend it with high-density polyethylene and use it as a mixed composition.

The cavity-containing stretched molded product of the present invention can be obtained by melt-extruding the above-mentioned composition into an unstretched original fabric, and then subjecting it to cross- or biaxial stretching.

This stretching method may be any of known uniaxial stretching methods such as roll stretching, hot plate stretching, and open stretching, or simultaneous or sequential biaxial stretching such as tubular stretching and tenter stretching. The temperature of the original film is maintained at a temperature at which the high-density polyethylene is substantially stretched and oriented, that is, a temperature below the crystalline melting point of the high-density polyethylene, and
In the case of uniaxial stretching, the stretching ratio is 2 times or more in either the vertical or horizontal direction, and in the case of biaxial stretching, the stretching ratio is 2 times or more in either the vertical or horizontal direction, preferably 4 in the area magnification.
Stretch it more than double. - In the case of axial stretching, it is particularly preferable to stretch to 4 times or more, and in the case of biaxial stretching, it is particularly preferable to stretch to an area magnification of 6 to 50 times. Countless voids (gaps) are formed inside the hollow stretched molded product of the present invention obtained in this way,
The apparent density is 0.92 or less, and the excellent one is o, 89
Below, the particularly excellent ones have a weight of 0.85 or less, which is significantly lighter than high-density polyethylene alone. Moreover, this molded product has excellent surface gloss, and in the case of a film or sheet-like molded product, it has opacity with a total light transmittance of 30% or less, and has a unique pearl-like luster.

In addition, when the composition is molded without stretching, no cavities are generated and the molded product is transparent or translucent, and its apparent density is higher than that of high-density polyethylene alone. Contrary to the purpose, void-containing moldings cannot be provided.

In addition, the cavity-containing stretch-molded product of the present invention may be heat-treated under tension or under several percent relaxation as necessary after being stretched in the same manner as ordinary stretched-molded products, or may be subjected to corona treatment in an atmosphere of air, oxygen, nitrogen, etc. Known surface treatments such as , plasma treatment, etc. can also be performed.

The high softening point petroleum resin used in the composition and production method of the present invention is one whose main component is a nclopentadiene monomer as a raw material. Specific raw materials include:
Cyclopentadiene, dicyclopentadiene, multimers thereof, alkyl substituted products thereof, or mixtures thereof, cyclopentadiene monomers from the by-product fraction when producing ethylene by thermally decomposing petroleum naphtha, etc. styrene, vinyltoluenes, α,β-methylstyrene that can be copolymerized with cyclopentadiene-based components; , vinyl aromatic hydrocarbons such as indene, alkyl-substituted indenes, and C9 fractions whose main components are the above-mentioned vinyl aromatic hydrocarbons, which are produced as by-products when producing ethylene by thermally decomposing petroleum naphtha. I'll come.

In addition, in the CPD fraction, most of the components other than the main cyclopentadiene component are saturated hydrocarbons that are inert to polymerization. May contain olefins, etc.
In the present invention, the lower the concentration is, the more desirable it is, and it is preferably 1/10 or less of the cyclopentadiene component in terms of weight.

The high softening point petroleum resin used in the molded article and manufacturing method of the present invention can be prepared by using the cyclopentadiene monomer or/and the CPD fraction alone, or by adding the above-mentioned vinyl aromatic hydrocarbon or/and The fractions C and C are mixed and thermally polymerized in the presence or absence of a solvent such as benzene, toluene, xylene, n-hexane or kerosene in an atmosphere of an inert gas such as nitrogen. The preferred polymerization conditions are a polymerization temperature of 220 DEG to 320 DEG C. and a polymerization time of 0.2 to 10 hours under a pressure that can maintain the molding system in a liquid phase.

In order to obtain a high softening point petroleum resin, either polymerization is carried out for a long time of 3 hours or more at a high temperature of 230°C or higher, or after the second stage polymerization is carried out, unreacted components and solvent are distilled off. Afterwards, under reduced pressure, etc., hold at a high temperature, preferably 230°C or higher, for a number of minutes,
It is preferable to perform multi-stage polymerization of two or more stages, such as performing a second-stage polymerization. In order to adjust the weight average molecular weight, a radical initiator or the like may be added to this reaction system. Such a series of polymerization reactions can be carried out in a batch, semi-batch or continuous manner. Further, after the polymerization reaction, it is desirable to subsequently lower the pressure of the polymerization system to remove unreacted components and inert components such as solvents in the raw materials.

The hydride of the high softening point cyclopentadiene petroleum resin used in the present invention can be obtained by further hydrogenating the high softening point cyclopentadiene petroleum resin by a conventionally known method. For example, by melting a high softening point cyclopentadiene petroleum resin and using a metal or metal oxide hydrogenation catalyst such as nickel, palladium, or cobalt,
Preferably a temperature of 150-300°C, 100-150°C
The hydride is obtained by hydrogenation under a hydrogen pressure of kg/C♂.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. The petroleum resins used in the following Examples and Comparative Examples and the evaluation methods for their characteristic values are as follows.

Cyclopentadiene petroleum resin (abbreviated as DCPD) A fraction consisting of 75% by weight of dicyclopentadiene and saturated hydrocarbons obtained by steam cracking of petroleum naphtha was heated in xylene in a nitrogen atmosphere by a known method. Hydrogenated product of cyclopentadiene petroleum resin obtained by thermal polymerization, removal of unreacted raw materials and solvent, and second stage polymerization by holding at a temperature of 200°C or higher for a certain period of time under reduced pressure, and then solidifying by cooling. (abbreviated as DCPD hydride): A hydrogenated resin obtained by hydrogenating the above DCPD by a known method described in the text was used.

Alicyclic resin: Alcon-140 manufactured by Arayo Kagaku Kogyo was used.

■Softening point (ring and ball method): Based on JIS K2207. However, if the softening point is 140°C or higher, the measurement is performed in a silicon bath. (Unit: °C) ①UV absorbance: o, 1 g of resin is dissolved in 100 ml of methylcyclohexane for spectroscopy, the ultraviolet absorption spectrum is measured, and the maximum value of the absorbance in the wavelength range of 265 to 276 nm is shown.

■Iodine value: According to JIS KOO70-1966.

The number of grams of iodine added to unsaturated components in 100 grams of sample is shown.

■Melt flow rate (MFR): J I 5
K7210-1976 test conditions 4 (190°C, 2.
16kgf). (Unit: g/10m1n) ■Density: Based on JIS K6760-1981 polyethylene test method 4.2.

(Unit: g/am3) ■Appearance is density: Measure the weight per molded product,
Value calculated per c+ff and divided by thickness em.

(Unit: g/am’) ■Total light transmittance: Based on JIS K6714.

(Unit: %) Examples 1 to 5, Comparative Examples 1 to 3 100 parts by weight of high-density polyethylene powder with a density of 0.957 and MFRl of 2, tris (2,4-di-t-butylphenyl) as an antioxidant 0.1 part by weight of phosphite,
0.2 parts by weight of calcium stearate and various petroleum resins shown in Table 1 were blended in predetermined amounts, mixed for 3 minutes using a Henschel mixer, then melt-kneaded at 200°C using a single-screw extruder, cooled, and then mixed. A predetermined composition was obtained by cutting.

Each of the obtained compositions was melt-extruded at 200°C using an extruder with a diameter of 40 mmφ and a T die, and cooled on a cooling roll kept at 90°C to obtain an unstretched raw sheet with a thickness of 0.5+nnk. . Next, the obtained raw sheet was cut into squares, and a pantograph type biaxial stretching machine was used to
4 in both vertical and horizontal directions at the same time at a temperature of ~120℃
The film was stretched twice and heat treated for 15 seconds while relaxing by 2% at the same temperature to obtain a biaxially stretched film.

As is clear from Table 1, the obtained films (Examples 1 to 5) all have extremely low density and low total light transmittance compared to films made only of high-density polyethylene, are lightweight, and are opaque. However, the films of Comparative Examples were all transparent and had high density, and were completely different from the films of Examples.

Example 6 To 100 parts by weight of high-density polyethylene powder with a density of 0.960 and MFRl of 0, the same amount of the antioxidant and calcium stearate used in Example 1 and 30 parts by weight of cyclopentadiene resin hydride were added. Blend and Example 1
In the same manner as above, a composition was obtained by melt extrusion at an extrusion temperature of 190°C, cooling and cutting to obtain a pelletized composition. The obtained composition was melt-extruded at 190°C using an extruder (bore diameter: 40 mmφ), an annular die, an air-cooled blown film forming apparatus equipped with a nearing and take-up/winding mechanism, and air-cooled during the nearing to form an unstretched original film ( Thickness: 100μ, folded diameter: 200mm
) was molded. This original fabric was slit to a width of 6 mm and stretched 6.0 times in the vertical direction at a temperature of 105°C on a hot plate.
The yarn was heat-treated on a roll at the same temperature and cooled to obtain a flat slit yarn. This yarn had an apparent density of 0.75 and was cloudy, and as a result of enlarging its cross section with a microscope, it was found that it contained numerous microscopic cavities.

〔Effect of the invention〕

The hollow-containing stretched molded product of the present invention retains the strength and rigidity characteristic of high-density polyethylene, is strong, lightweight, opaque, and has an excellent pearl-like luster, and can be used in films, sheets, tapes, yarns, and fibers. It can also be used in a wide range of applications, such as hollow containers, packaging materials, decorative materials, packaging materials, synthetic paper, and nonwoven fabrics. Furthermore, the manufacturing method is industrially excellent.

Claims (6)

[Claims] (1) At least one composition is prepared by blending 5 to 150 parts by weight of a high softening point petroleum resin with a softening point (ring and ball method) of 160 to 220°C to 100 parts by weight of high density polyethylene having a density of 0.94 or more. Apparent density after stretching in the direction: 0.92
A cavity-containing stretch-molded product which is as follows. (2) The high softening point petroleum resin is a cyclopentadiene petroleum resin, a hydride of a cyclopentadiene petroleum resin, or a mixture of a cyclopentadiene petroleum resin and its hydride, and contains 70% by weight or more of a cyclopentadiene component. The cavity-containing stretch-molded product according to claim 1. (3) The high softening point petroleum resin has a cyclopentadiene component of 70%
A cavity-containing stretch molded product which is a hydrogenated product of a cyclopentadiene petroleum resin containing at least % by weight, a softening point of 170 to 200°C, a UV absorbance of 0.8 or less, and an iodine value of 30 or less. (4) Melt a composition obtained by blending 5 to 150 parts by weight of a high softening point petroleum resin with a softening point (ring and ball method) of 160 to 220°C to 100 parts by weight of high-density polyethylene having a density of 0.94 or more. A method for producing a hollow-containing stretched product, which comprises forming an unstretched original fabric by extrusion, and then stretching it twice or more in at least one direction at a temperature below the crystal melting point of the high-density polyethylene. (5) The high softening point petroleum resin is a cyclopentadiene petroleum resin, a hydride of a cyclopentadiene petroleum resin, or a mixture of a cyclopentadiene petroleum resin and its hydride, and contains 70% by weight or more of a cyclopentadiene component. 5. The method for producing a cavity-containing stretch-molded product according to claim 4. (6) The high softening point petroleum resin contains 70% by weight or more of a cyclopentadiene component, has a softening point of 170 to 200°C, and has a UV
5. The method for producing a cavity-containing stretched molded article according to claim 4, which is a hydride of a cyclopentadiene petroleum resin having an absorbance of 0.8 or less and an iodination value of 30 or less.