JPH0637076B2 - Opaque stretched molded article and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to a stretch-molded article containing a polypropylene resin as a main component. More specifically, by stretching a composition obtained by adding a specific petroleum hydrocarbon resin to crystalline polypropylene,
A large number of minute cavities are generated inside or on the surface of the molded product,
The present invention relates to a stretched molded article imparted with an opaque or pearly feeling and a method for producing the same.

[Conventional technology]

Generally, a molded article having a pearly feeling or an opaque feeling is used, for example, as a uniaxially or biaxially stretched film in general packaging materials, decorative materials, synthetic papers, calligraphic printing papers, and the like.
It is also widely used as a tape, ribbon or filament for packing materials, woven yarns and the like.

Conventionally, as a method for making a molded article pearlized or opaque, (1) a method of adding a glossy substance such as a white pigment, an extender pigment or pearl essence, (2) a foaming agent is added at the time of molding to generate a large number of bubbles. Forming method, (3) a method of adding a large amount of an inorganic filler as described in JP-B-63-24532, JP-A-63-117043 and the like, followed by stretching to form a void, (4) There is known a method of treating a molded product with a solvent, a chemical or the like to form a dull product.

However, these methods have the following drawbacks. That is, regarding (1), it is necessary to use different pigments for opacification and pearlization, and pearl essence is also very expensive. In addition, a mixing method and apparatus that take into consideration the dispersion of these pigments are required. Regarding (2), it is necessary to select a foaming agent depending on molding conditions and applications, and it is difficult to obtain uniform fine foaming with a thin film such as a film. Regarding (3), since a large amount of inorganic filler is added, the fluidity at the time of extrusion is greatly reduced, the screen pack is clogged, and moisture absorption / foaming and poor dispersion due to the inorganic filler occur. It is easy and there are many troubles during production, such as replacement of the resin takes a long time. The obtained product also has drawbacks such as a decrease in glossiness and only a roughened surface can be obtained. In addition, (4) is a post-treatment process and requires a process for removing solvents and chemicals, which is disadvantageous in terms of equipment and cost. Also, the product has a pearly feel although it has a dull feel. There is a problem that can not be obtained.

[Problems to be Solved by the Invention]

An object of the present invention is to solve the above-mentioned conventional drawbacks, to provide a stretched molded product having excellent opacity, pearly feeling, and the like, being lightweight, and having a high gas permeability, and further to provide a foam for production. An object of the present invention is to provide a method for producing an opaque stretch-molded article that does not have difficulty in production such as non-uniformity and poor dispersion.

[Means for Solving the Problems]

As a result of intensive studies to solve the above-mentioned problems, the present inventors have drawn a composition in which a specific amount of a specific cyclopentadiene-based petroleum resin is added to polypropylene under a specific condition to obtain an excellent opacity. The present invention has been completed by obtaining a stretched molded product having a light weight and a high gas permeability.

That is, the present invention provides (1) 3-4 parts of cyclopentadiene-based petroleum resin and / or hydrogenated cyclopentadiene-based petroleum resin having a softening point (ring and ball method) of 160 ° C. or higher with respect to 100 parts by weight of polypropylene.
A composition in which 0 parts by weight is blended is stretched in at least one direction and has a total light transmittance of 50% or less and a density of 0.8.
It is an opaque stretched molded product of 9 or less, and (2) cyclopentadiene-based petroleum resin and / or hydrogenated cyclopentadiene-based petroleum having a softening point (ring and ball method) of 160 ° C. or higher with respect to 100 parts by weight of crystalline polypropylene. It is characterized in that a composition containing 3 to 40 parts by weight of a resin is formed into a raw sheet by a melt extrusion method, and then stretched at least twice in at least one direction at a temperature not higher than the softening point of the petroleum resin. The present invention relates to a method for producing a stretch-molded product.

The crystalline polypropylene used in the present invention is a homopolymer of propylene, a copolymer with other α-olefin containing propylene as a main component, or a mixture thereof.

Cyclopentadiene-based petroleum resin used in the present invention, cyclopentadiene obtained from steam cracking of petroleum naphtha, dicyclopentadiene and its multimers or their alkyl-substituted fractions or mixtures thereof as a main component In the presence or absence of a solvent, under an atmosphere of an inert gas such as nitrogen gas, preferably at a temperature of 220 to 320 ° C., under a pressure at which the polymerization system can be maintained in a liquid phase, for several hours or more. Cyclopentadiene-based petroleum resin obtained by thermal polymerization, and a method known in the art for the petroleum resin, that is, using a catalyst such as a metal such as palladium, nickel, cobalt or an oxide thereof, in the presence of a solvent.
A hydrogenated cyclopentadiene-based petroleum resin or a mixture thereof which is hydrogenated under the conditions of a temperature of 50 to 300 ° C. and a hydrogen pressure of 10 to 150 kg / cm ² . The cyclopentadiene fraction may naturally include diolefins such as butadiene, isoprene and piperylene, and monoolefins such as butene and pentene. The fraction may be polymerized in a single stage,
For example, dicyclopentadiene may be polymerized in two or more stages such as in two stages, and the polymerization process, the polymerization and the hydrogenation process may be either continuous or batch.

Among the cyclopentadiene-based petroleum resins thus obtained, their softening point (ring and ball method) is 160 in the present invention.
Must be above ℃. If the softening point does not reach 160 ° C, both the opaqueness and the pearly feeling are insufficient, and the stretch-molded article aimed at by the present invention cannot be obtained.
Similar to JP-A-61-203140 and the conventionally known hydrogenated petroleum resin, the direction of the invention is completely opposite, that is, the molded product tends to be transparent and tends to improve the barrier property. It is impossible to obtain a stretch-molded product which is opaque, has minute voids, and is permeable to gas and which is very characteristic.

In the present invention, a hydrogenated cyclopentadiene-based petroleum resin having a softening point of 160 ° C. or higher is preferable, and a softening point of 170 to
A hydrogenated cyclopentadiene-based petroleum resin having a iodine value of 20 or less at 200 ° C. has excellent compatibility with polypropylene, can be stably processed, and can obtain a stretched molded article excellent in whiteness and opacity, and particularly, preferable.

The composition used in the present invention is a cyclopentadiene-based petroleum resin or a hydrogenated cyclopentadiene-based petroleum resin having a softening point of 160 ° C. or higher with respect to 100 parts by weight of polypropylene, or a mixture thereof (simply referred to as cyclopentadiene-based petroleum resin). Is mixed in an amount of 3 to 40 parts by weight. If the amount of the petroleum resin added is less than 3 parts by weight, the effect of imparting opacity, which is the object of the present invention, is insufficient, and if it exceeds 40 parts by weight, extrusion unevenness and stretch rupture tend to occur during molding, resulting in extremely low productivity. , Not preferable.

In order to obtain an opaque stretched molded article having excellent productivity, the hydrogenated petroleum resin having a softening point of 170 to 200 ° C. is added to 5 to 3 parts.
It is particularly preferable to add it in the range of 0 parts by weight.

In the composition of polypropylene and cyclopentadiene-based petroleum resin used in the present invention, if necessary, various additives known to be added to polypropylene, such as processing stabilizers, antioxidants, lubricants, slip agents, You may mix | blend an antistatic agent and various polymers.

The method for producing this composition can be easily obtained by mixing with an ordinary blender or mixer, but it is particularly preferable to melt-mix with an extruder, Banbury mixer or the like to use as a pelletized composition. preferable. It is also useful to add a large amount of the petroleum resin to polypropylene or other resin, form a masterbatch, and then mix with polypropylene to use as a mixed composition.

The composition thus obtained is used to prepare a raw sheet by a melt extrusion method, and then uniaxially or biaxially stretched by a known method to obtain a molded article having an opaque or pearly feel which is the object of the present invention. .

This stretching method may be any known method such as roll stretching, oven stretching, known uniaxial stretching method such as hot plate stretching or tubular stretching, simultaneous or sequential biaxial stretching such as tenter method stretching, It is necessary that the raw fabric temperature at the time of stretching be equal to or lower than the softening point of the petroleum resin in the composition used, and the total light transmittance of the stretched molded product obtained by selecting these conditions is 50% or less. An opaque stretched molded product having a density of 0.89 or less is obtained.

In the case of stretching in an oven, the hot air temperature may be set above the melting point of polypropylene, but it is not possible to stretch and orient polypropylene above the melting point. This is because the actual temperature of the drawn raw fabric has not reached the melting point due to the relationship between the thickness of the
In the present invention, the actual temperature of the original stretched fabric is referred to as the stretching temperature.

A stretched molded article aimed at by the present invention can be obtained by stretching at least two times in at least one direction at a stretching temperature not higher than the softening point of the petroleum resin used for the composition. Simultaneous or sequential biaxial stretching in which high-area stretching with an area magnification of about 10 to 60 times is particularly preferable. Incidentally, the scale of the stretch ratio as a stretch-molded product is usually the difference between the refractive index in one of the longitudinal and transverse directions and the refractive index in the thickness direction when a polypropylene-only stretch-molded product is measured by a known method. That is, a stretching ratio of (refractive index in longitudinal direction or lateral direction-refractive index in thickness direction) ≧ 500 × 10 ⁻⁴ is preferable.

The unstretched molded product obtained by molding the composition used in the present invention without stretching gives only a cloudy translucent molded product having a degree of slightly decreased transparency, and since the density is higher than that of polypropylene alone, The molded object aimed at by the invention cannot be obtained.

The stretched molded product obtained in the present invention has a total light transmittance of 5
Characteristic is that the density is 0% or less and the density is 0.89 or less,
If the total light transmittance exceeds 50%, the opaqueness is insufficient, and if the density exceeds 0.89, internal foaming is insufficient, and a stretch-molded product with a pearly feeling cannot be obtained. Stretch-molded products having a total light transmittance of 40% or less and a density of 0.80 or less are excellent in opacity, light-shielding property and pearl luster, and are particularly preferable.

The stretch-molded product obtained in the present invention, if necessary, air,
Surface treatment such as corona treatment and plasma treatment can also be performed in an atmosphere of oxygen, nitrogen or the like.

〔Example〕

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples. The characteristic values used in the following examples and comparative examples were evaluated by the following methods.

(1) Softening point (ring and ball method): According to JIS K2207. However, when the softening point is 140 ° C. or higher, the measurement is performed in a silicone oil bath. (Unit: ° C) (2) Iodine value: According to JIS K0070-1966.
It refers to the number of grams of iodine added to unsaturated components in 100 g of a sample.

(3) Density: A value obtained by measuring the weight per 1 m ^{2 of the} molded product, converting it per 1 cm ² , and dividing by the thickness cm.

(Unit: g / cm ³ ) (4) Total light transmittance: According to JIS K-6714.

(5) Haze: According to ASTM D1003.

(6) MFR (melt flow rate): JIS K721
Test condition 14 of 0-1776 (230 ° C, 2.16 kg
According to f). (Unit; g / 10 min.) (Examples 1 to 8) MFR 1.5, 100 parts by weight of crystalline polypropylene powder containing 92% by weight of an insoluble part in n-heptane, and phenol antioxidant BHT 0 .1 part by weight,
0.1 parts by weight of calcium stearate and a predetermined amount of cyclopentadiene-based petroleum resin or its hydride shown in Table 1 were added, mixed with a Henschel mixer, melt-mixed at 240 ° C. through an extruder, cooled and cut. A pelletized composition was obtained. Each of the obtained compositions was heated to 250 ° C. using an extruder having a diameter of 40 mm and a T-die having a width of 30 cm.
Was melt extruded at a temperature of 4 ° C., and rapidly cooled by a mirror surface cooling roll kept at 45 ° C. to obtain an unstretched raw sheet having a thickness of 1.1 mm. Table 1 shows the density of the obtained raw sheet. Next, this raw sheet was cut into squares, preheated at a temperature of 155 ° C. for 70 seconds using a pantograph-type biaxial stretching machine, and then stretched 5.2 times in both vertical and horizontal directions at the same temperature. Then, heat treatment was performed under tension at the same temperature for 15 seconds to obtain eight kinds of biaxially stretched films having a thickness of about 40μ. The characteristic values of the obtained film are also shown in Table 1.

The cyclopentadiene-based petroleum resin was obtained by polymerizing cyclopentadiene or dicyclopentadiene obtained by steam cracking of naphtha by a commonly known method. In addition, hydrogenation is performed using a nickel-based catalyst.
What was obtained by carrying out at 50 ° C. under a hydrogen pressure of 80 kg / cm ² was used.

As is apparent from Table 1, Examples 1 to 1 according to the present invention
The film of No. 8 has a high haze value, a low total light transmittance, and a density that is significantly lower than that of the raw sheet, has many fine voids formed inside the film, and is opaque and has a unique pearl luster. Has become.

(Comparative Examples 1 to 5) Comparative Examples 1 to 8 are the same as those of Examples 1 to 8 except that the cyclopentadiene-based petroleum resin is not added, and the cyclopentadiene-based petroleum resin is added. Other than blending the one having a softening point of less than 160 ° C., the case of treating under the same conditions is shown in Table 1 as Comparative Examples 2 to 5, but the film is transparent and has a high density. It can be seen that opacity cannot be imparted and the film becomes completely different.

(Comparative Example 6) MFR 4.0, 100 parts by weight of crystalline polypropylene powder containing 93% by weight of an insoluble portion in n-heptane, was added as an additive with a phenolic antioxidant (Irganox 1010 manufactured by Ciba-Geigy Co.). 10 parts by weight, phosphorus antioxidant (Mark PEP-Q manufactured by ADEKA ARGUS CORPORATION) 0.05 part by weight, calcium stearate 0.1 part by weight, erucic acid amide 0.12 part by weight and softening point (ring and ball method) 176 ° C. ,
15 parts by weight of hydrogenated dicyclopentadiene-based petroleum resin powder having an iodine value of 8 was blended, mixed for 2 minutes with a Henschel mixer, and then melt-kneaded at 220 ° C. using a same-direction twin-screw extruder, followed by cooling, After cutting, a pelletized composition was obtained.

The obtained composition is melt extruded at 230 ° C. using a single-screw extruder having a diameter of 65 mm and a T-die having an effective width of 600 mm.
The film was cooled using a rough surface cooling roll having a diameter of 400 mm kept at 5 ° C. and wound at a speed of 30 m / min to obtain an unstretched film having a width of 400 mm and a thickness of 30 μ.

The resulting unstretched film had a density of 0.90 and a haze of 5.
5, it was a transparent type film with a total light transmittance of 88% and a slight turbidity, but an object could be seen through the film, and it was revealed that the unstretched film could not be opaque.

(Example 9) The same composition as used in Comparative Example 6 was used, and the caliber was 65 mm.
A φ single-screw extruder and a T-die having an effective width of 300 mm were used for melt extrusion, followed by rapid cooling with a mirror surface cooling roll kept at 25 ° C. to obtain a raw sheet having a thickness of 0.15 mm and a density of 0.91. This raw sheet is preheated with four preheating rolls having a diameter of 300 mmφ and kept at 120 ° C., and then stretched by 5.2 times in the vertical direction by a nip roll kept at the same temperature, while relaxing about 3%,
It was heat-treated in a hot air bath at 140 ° C. and then rapidly cooled with a cooling roll at 30 ° C. to obtain a uniaxially stretched film having a thickness of 30 μ.

The obtained uniaxially stretched film has a density of 0.78 and a haze of 9.
It was a beautiful film having an opaque pearl luster with 2% and a total light transmittance of 25%.

〔The invention's effect〕

The stretched molded products such as films, yarns, filaments, and hollow containers obtained by stretch-blow obtained in the present invention make use of their opacity, light-shielding property, weight reduction and unique pearl luster, etc. for general packaging materials, decorative materials, synthetic papers. It is useful for a wide range of applications such as, packaging materials, and woven yarn.

The opacifying agent blended in the present invention is a resin and can be melt-mixed, so that it can be uniformly dispersed, and there are no problems such as poor dispersion or non-uniform foaming as a manufacturing method, and stretching similar to polypropylene itself. It can be molded without any special post-treatment process. It is also an excellent manufacturing method.

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Claims (2)

[Claims] 1. At least one composition containing 3 to 40 parts by weight of cyclopentadiene-based petroleum resin and / or hydrogenated cyclopentadiene-based petroleum resin having a softening point (ring and ball method) of 160 ° C. or higher with 100 parts by weight of polypropylene. An opaque stretch-molded product that is stretched in the same direction and has a total light transmittance of 50% or less and a density of 0.89 or less. 2. A composition in which 3 to 40 parts by weight of a cyclopentadiene-based petroleum resin having a softening point (ring and ball method) of 160 ° C. or higher and / or a hydrogenated cyclopentadiene-based petroleum resin is mixed with 100 parts by weight of crystalline polypropylene. A method for producing an opaque stretched molded article, which comprises forming a raw sheet by a melt extrusion method, and then stretching the sheet at least twice in at least one direction at a temperature not higher than the softening point of the petroleum resin.