JP2003311807A - Polypropylene resin foamed sheet, laminated foamed sheet using the same, and manufacturing method for molded container and foamed sheet from them - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polypropylene resin foamed sheet excellent in moldability and secondary processability, a polypropylene resin laminated foamed sheet obtained by laminating a polypropylene resin non-foamed layer to the foamed sheet and a molded container obtained by thermal molding of these sheets. <P>SOLUTION: The polypropylene resin foamed sheet has a mean thickness of 1-5 mm, a value obtained by dividing the difference between the maximum and minimums values of thickness by the mean thickness of 0.20 or less, a closed-cell ratio of 60% or more and a density of 0.1-0.5 g/cc and is characterized in that the number of cells per a unit area is 30 cells/mm<SP>2</SP>or more and the cyclic number of times of cyclic thin-walled parts looked in the width direction of the sheet is 30 times/m or more. The polypropylene resin laminated foamed sheet is obtained by laminating a polypropyrene resin non-foamed layer on at least the single layer of the foamed sheet. The molded container is obtained by thermoforming the foamed sheet or the laminated foamed sheet and the difference between the maximum and minimum values of the thickness of the side part of the molded container is not more than 0.5 mm. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polypropylene resin foam sheet having excellent moldability, a laminated foam sheet using the same, a molded container made of the same, and a method for producing the foam sheet.

[0002]

2. Description of the Related Art Foamed sheets made of a thermoplastic resin are generally light in weight, have good heat insulating properties and good buffering properties against external stress, and can be formed by heating secondary molding such as vacuum forming. Since a molded product can be easily obtained, it is widely used mainly for polystyrene resins and polyethylene resins as cushioning materials, food containers, heat insulating materials, automobile members and the like. In particular, polystyrene-based resin foamed sheets are widely used in containers for instant noodles, etc., because of their excellent moldability.

On the other hand, a polypropylene resin foam sheet is used as a container for microwave oven cooking because it has excellent heat resistance and oil resistance due to the characteristics of the base resin and is easily heat-molded.

In the production of polypropylene resin extruded foamed sheets, a method of extruding resin from a circular die having an annular slit to obtain a foamed sheet is generally used. However, since the circular die has a structure of an annular slit, it is necessary to have a structure for supporting the inner side of the slit (inner cylindrical portion). Therefore, the resin that has flowed into the circular die is divided by the structure that supports the inner cylinder, after which the resin coalesces, and is extruded from the annular slit, the divided resin,
The resin is extruded with the history of the blocked flow remaining, and the extruded resin has streaks and uneven thickness due to the division.

On the other hand, in a polypropylene resin foamed sheet molded container, a portion of the container where the sheet is stretched at the time of molding tends to be thin. This is because in the case of the polypropylene-based resin foam sheet, the increase in thickness during secondary foaming is low.

The secondary foaming is a phenomenon in which the gas in the bubbles expands due to heating during molding and the base resin melts to expand the bubbles, resulting in foaming and an increase in thickness. When the increase in thickness at the time of secondary foaming is small, that is, when the increase in thickness at the time of heat molding is small, it is difficult to secure the thickness of the portion where the stretching is large.

Japanese Unexamined Patent Publication (Kokai) No. 5-338055 discloses a foamed sheet which defines a ratio between the maximum thickness and the minimum thickness in the width direction of the foamed sheet, thereby obtaining a molded product with less uneven thickness.

However, when the foamed sheet before heat molding has a thin portion (thin portion), the thin portion may be further thinned (thinned) by stretching during molding. This is because the stress at the time of stretching is concentrated on the thin portion, and the stress remarkably appears on the side portion of the container where the molding and stretching are large. In particular, when the number of thin portions of the foamed sheet is small, the number of thin portions entering the container side portion is small. As described above, when the number of thin portions in the container side portion is small, the stress concentrated on the thin portions due to the molding and stretching becomes large. As a result, there is a problem in that the thickness of the stretch-molding is extremely advanced, resulting in a molded container having an extremely thin portion. Further, it is difficult to perform molding so that such a thin portion does not occur.

Further, in Japanese Patent Laid-Open No. 6-906, the polypropylene resin foamed sheet has coarser air bubbles than the polystyrene resin, but in order to improve the drawbacks caused by this, a polypropylene resin is laminated. , A method for obtaining a polypropylene-based resin laminated foam sheet excellent in appearance and the like is disclosed.

However, when the polypropylene resin film is laminated on the polypropylene resin foam sheet having coarse bubbles by thermal lamination, the film layer is liable to peel off or swell during the molding and heating of the obtained laminated foam sheet. This is because when the bubbles in the foam sheet are coarse (when the number of bubbles per unit area is small), the unevenness of the bubbles on the surface is large and the film is laminated with air in the recesses, and the air expands during molding heating. This is because the film swells.

As described above, according to the conventional technique, a molded product having less unevenness in thickness can be obtained, and a laminated foam sheet having good moldability can be obtained. Good moldability and secondary processability (lamination of films) are obtained. It is difficult to obtain a polypropylene-based resin foam sheet having the same.

[0012]

The present invention provides a polypropylene resin foam sheet having excellent moldability and secondary processability, and a molded article obtained by heat molding the foam sheet, and more specifically, By adjusting the properties and thickness characteristics of the polypropylene-based resin foamed sheet to a specific range, the polypropylene-based resin foamed sheet having excellent moldability and suitable for obtaining a laminated sheet, and the thickness unevenness obtained by molding the foamed sheet It is an object of the present invention to provide a molded container having a small amount. It is another object of the present invention to provide a polypropylene-based resin laminated foamed sheet having excellent moldability and a polypropylene-based resin laminated foamed molded container obtained by thermoforming the laminated foamed sheet.

The present inventors have conducted intensive studies to solve the above-mentioned problems of the prior art and achieve the above-mentioned object, and as a result,
By designing the structure of the circular die used during the production of the polypropylene-based resin foam sheet to be a specific number, and making the number of periodic thin portions of the resulting foam sheet a specific number of times, and specifying the properties of the foam sheet, molding It has been found that a foamed sheet having good properties and good secondary workability can be obtained, and has completed the present invention.

That is, the present invention has an average thickness of 1 to 5 m.
m, the value obtained by dividing the difference between the maximum value and the minimum value of the thickness by the average thickness is 0.20 or less, the closed cell ratio is 60% or more, and the density is 0.
A polypropylene resin foam sheet of 1 to 0.5 g / cc, in which the number of bubbles per unit area is 30 cells / mm ² or more, and the number of cycles of the periodic thin portion seen in the width direction of the sheet is 30 times. / M or more, the polypropylene resin foam sheet (Claim 1), the base resin of the polypropylene resin foam sheet, obtained by melt-kneading the raw material polypropylene resin, isoprene and radical polymerization initiator A polypropylene-based resin foamed sheet according to claim 1 (claim 2) which is a modified polypropylene-based resin, and a polypropylene-based resin non-foamed layer laminated on at least one surface of the polypropylene-based resin foamed sheet according to claim 1 or 2. Polypropylene resin laminated foam sheet (claim 3), characterized in that
A molded container obtained by thermoforming the polypropylene-based resin foamed sheet according to claim 1, wherein the difference between the maximum value and the minimum value of the side thickness is 0.5 mm or less (claim 4). ), A molded container obtained by thermoforming the polypropylene-based resin laminated foam sheet according to claim 3,
The difference between the maximum value and the minimum value of the lateral thickness is 0.5 mm or less, and a molded container (claim 5) and a circular die having an annular slit are used to extrude a foamed sheet and polypropylene. When manufacturing a resin foam sheet, a portion of the inner cylindrical support structure that supports the inner portion of the circular slit of the circular die (inner tubular portion) and divides the polypropylene resin flow passage is located outside the annular slit. A method for producing a polypropylene-based resin foam sheet according to claim 1, characterized in that a circular die having at least 30 locations in the circumferential direction of the circular die that are directly bonded to the (outer cylinder portion) is used. .

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The polypropylene-based resin foam sheet of the present invention has an average thickness of 1 to 5 mm, further 1 to 3 m.
m. If the average thickness is too thin, the heat insulating properties, rigidity and cushioning properties are poor, and if it is too thick, the moldability is poor.

In the polypropylene-based resin foamed sheet of the present invention, the value obtained by dividing the difference between the maximum value and the minimum value of the thickness by the average thickness is 0.2 or less. If the value obtained by dividing the difference between the maximum value and the minimum value of the thickness by the average thickness is too large, the thickness unevenness of the molded product obtained by heat-molding the foamed sheet is large, and a good molded product cannot be obtained. There are cases.

The thickness of the polypropylene resin foam sheet of the present invention can be measured as follows.

That is, 10 mm in the width direction of the foam sheet.
Provide measurement points at intervals. The thickness of the foamed sheet at each measurement point is measured by a thickness gauge (for example, tecloc).
k) Measured by a thickness gauge manufactured by the company. The arithmetic average of the respective measurement points is calculated and used as the average thickness of the foamed sheet. Also,
The maximum value and the minimum value are the maximum value and the minimum value of the thickness.

The closed cell ratio of the polypropylene resin foam sheet of the present invention is 60% or more, further 70% or more. If the closed cell ratio is too small, the rigidity of the molded container obtained by heat molding may be poor.

The polypropylene-based resin foam sheet of the present invention has a density of 0.1 to 0.5 g / cc, more preferably 0.13.
~ 0.3 g / cc. If the density is too low,
The rigidity is poor, and when it is too large, the heat insulating property is poor.

The polypropylene resin foam sheet of the present invention has a cell number of 30 cells / mm ² or more, and further 50 cells / m.
m ² or more. When the number of cells is too small, swelling of the film occurs during molding and heating of the laminated foam sheet obtained by laminating films, and it becomes difficult to obtain a good molded product.

The number of bubbles in the polypropylene resin foam sheet of the present invention can be measured as follows.

That is, the foamed sheet is cut in the width direction,
Measuring units are provided at intervals of 50 mm in the width direction. Number of bubbles in the thickness direction in the cross section of each measurement part: S1 (number) and 5 in the width direction
The number of bubbles in the width direction between mm: S2 (cells / 5 mm) is measured. Next, each measurement part was cut in the extrusion direction, and the number of bubbles within 5 mm in the extrusion direction of the cross section: S3 (cells / 5 m
m) is measured. After measurement, the number of bubbles in each measurement part: S
0 (S0 = S1 × S2 × S3 / 25 (cells / mm ² )) is obtained, and the arithmetic mean of the number of cells: S0 in all the measurement parts is obtained and taken as the number of bubbles.

The polypropylene-based resin foamed sheet of the present invention is used for the purpose of obtaining a desired cell structure, for example, by extruding and foaming and then promoting cooling by blowing air,
It may be stretched when it is taken up by the mandrel.

In the polypropylene-based resin foamed sheet of the present invention, the number of periodic thinned portions seen in the width direction of the sheet is 30 times / m or more, further 40 times / m or more.
The upper limit is about 80 times / m from the viewpoint of difficulty in processing the supporting structure of the die due to the thin portion. If the number of cycles of the thin portion is too small, the molded product obtained by heat molding tends to have uneven thickness.

The periodic thin portion will be described.

Measuring points are provided at intervals of 10 mm in the width direction (direction orthogonal to the extrusion direction) of the foamed sheet to measure the thickness. At this time, in an arbitrary measurement point and a measurement point adjacent thereto, a portion where the measurement point is thinner than two measurement points adjacent thereto is referred to as a thin portion. A state in which such thin portions periodically exist in the width direction of the sheet is called a periodic thin portion. By counting the number of thin portions from the measurement result of the thickness and dividing by the width of the sheet, the number of cycles of the thin portions can be obtained periodically.

The periodic thin portion in the present invention is adjusted by adjusting the number of the structural portions that support the inner tubular portion of the circular die and divide the resin flow passage and are directly coupled to the outer tubular portion. can do.

Of the structural parts that support the inner cylindrical portion of the circular die and divide the resin flow passage, those that are directly coupled to the outer cylindrical portion refer to the inner cylindrical portion of the circular die that forms the resin flow passage. This is the number of the inner tubular portion support structure portions that are directly coupled to the outer tubular portion for holding, and does not include those that are not directly coupled to the outer tubular portion. The sectional shape of the divided resin flow path in the direction perpendicular to the flow direction is not particularly limited. By increasing the number of divided portions, it is possible to increase the number of cycles of the periodic thin portion.

FIG. 1 shows an example of the result of measuring the sheet thickness in the width direction. From FIG. 1, it can be seen that the sheet thickness periodically changes in the width direction. One period of the thin portion is from the valley of thickness to the next valley.

FIG. 2 shows an example of the inner cylindrical portion supporting structure portion in the circular die. In FIG. 2, 1 is an inner cylindrical portion, 2 is an annular slit, 3 is a resin flow direction, 4 is a resin flow passage, and 6 is a resin flow passage dividing portion (12 places) directly coupled to the outer cylinder portion 7.

It should be noted that the number of resin flow path dividing portions in FIG. 2 and the number of thin portions of the sheet thickness in the width direction are substantially the same, but uneven flow of the resin occurs in the die, and the thin portions overlap. Probably because of this, a difference of 1 to 2 may be used between the number of resin flow path dividing portions and the number of thin portions of the sheet thickness in the width direction.

FIG. 3 shows a cross section taken along the line AA in FIG. Reference numeral 5 in FIG. 3 is an inner cylinder support structure portion, and 6 is directly coupled to the outer cylinder portion 7.

In FIG. 3, the resin flow passage 4 is doubled inside and outside, and the resin flow passage dividing portion is also doubled. However, the outer resin flow passage dividing portion 6 is thin for the following reason. Cause the department.

That is, the inside of the foamed tubular sheet extruded from the die is brought into contact with the cooling tube to be smoothed,
Leveled, but the outside is not smoothed and leveled. Therefore, the resin flow path dividing portion involved in the formation of the thin portion becomes the outer resin flow path dividing portion 6, and therefore, among the structural portions that divide the resin flow passage, those that are directly coupled to the outer cylindrical portion 7 It is specified that a circular die having a number of 30 or more is used.

Since the resin extruded from the die is usually stretched to about 1000 mm in the width direction, the number of the resin directly bonded to the outer cylinder portion 7 is about 1 mm per width of the foamed sheet.

As the polypropylene resin of the base resin used for producing the polypropylene resin foamed sheet of the present invention, a linear polypropylene resin (hereinafter, this polypropylene resin is referred to as "raw polypropylene resin"). Which has long chain branching by irradiating with electron beam (for example, HMS-P manufactured by Sun Allomer Co.)
P) or a modified polypropylene resin obtained by melt-kneading a raw material polypropylene resin, an isoprene monomer and a radical polymerization initiator is preferable from the viewpoint of excellent foamability. Particularly, a modified polypropylene resin obtained by melt-kneading a raw material polypropylene resin, an isoprene monomer and a radical polymerization initiator is preferable from the viewpoint of easy production.

As the raw material polypropylene resin,
Examples thereof include crystalline polymers such as propylene homopolymers, block copolymers of propylene and other monomers, and random copolymers of propylene and other monomers. The propylene homopolymer is preferred from the viewpoint of high rigidity and low cost, and the block copolymer of propylene and other monomers is preferred from the viewpoint of high rigidity and high impact resistance. When the raw material polypropylene resin is a block copolymer of propylene and another monomer or a random copolymer of propylene and another monomer, high crystallinity and high rigidity characteristic of the polypropylene resin. From the viewpoint of maintaining good chemical resistance, the propylene monomer component contained is 75% of the total.
It is preferably not less than wt% (hereinafter referred to as%), and more preferably not less than 90%.

Examples of the other monomer copolymerizable with the propylene include monomers such as ethylene, α-olefin, cyclic olefin, diene monomer and vinyl monomer. These may be used alone,
You may use it in combination of 2 or more type. Of these, butene-1 of ethylene or α-olefins is preferable because it is inexpensive.

The molecular weight (weight average molecular weight) of the raw material polypropylene resin is preferably 50,000 to 2,000,000 from the viewpoint of industrial availability, and 100,000 to 1,000,000 from the viewpoint of low cost. Is preferred.

If necessary, other resin or rubber may be added to the raw material polypropylene resin within a range not impairing the effects of the present invention. The addition amount of the other resin or rubber to the raw material polypropylene resin varies depending on the type of the other resin or rubber, but as long as it does not impair the effects of the present invention as described above, it is usually 25%. It is below the level.

The modified polypropylene resin is produced by melt-kneading a raw material polypropylene resin, an isoprene monomer, another vinyl monomer copolymerizable with the isoprene monomer, and a radical polymerization initiator. It may have been done.

When the above isoprene monomer and another vinyl monomer copolymerizable therewith are used in combination, the amount of the other vinyl monomer copolymerizable with the isoprene monomer is equal to the amount of the isoprene monomer. For 100 parts by weight of the body (hereinafter referred to as "parts"),
It is preferably 100 parts or less, more preferably 75 parts or less. If the amount of the other vinyl monomer copolymerizable with the isoprene monomer used is too large, the viscosity of the modified polypropylene resin obtained may decrease, and the foamability may decrease.

The amount of the isoprene monomer to be melt-kneaded (the total amount of the isoprene monomer and the other vinyl monomer copolymerizable with the isoprene monomer, the same applies hereinafter) is the raw material. For 100 parts of polypropylene resin,
It is preferably 0.1 to 20 parts, more preferably 0.3 to 10 parts. When the amount of the isoprene monomer used is less than the above range, the foaming property of the modified polypropylene resin may decrease. On the other hand, if it exceeds the above range, the heat resistance and rigidity, which are the characteristics of the polypropylene resin, may be impaired.

Examples of the radical polymerization initiator include, but are not limited to, peroxides generally used as radical polymerization initiators.

Preferred examples of the peroxide include organic peroxides such as ketone peroxide, peroxyketal, hydroperoxide, dialkyl peroxide, diacyl peroxide, peroxydicarbonate and peroxyester. To be These may be used alone or in combination of two or more. Among these, those having high hydrogen abstraction ability, such as dialkyl peroxide and peroxyester, are preferable.

The radical polymerization initiator is used in an amount of 0.1 to 10 parts, based on 100 parts of the raw material polypropylene resin, from the viewpoint that the modified polypropylene resin has good foamability and is economical. Further, it is preferably 0.2 to 5 parts.

The raw material polypropylene resin may include an antioxidant, a metal deactivator, a phosphorus processing stabilizer, if necessary,
UV absorber, UV stabilizer, optical brightener, metal soap,
Stabilizers such as antacid adsorbents, crosslinking agents, chain transfer agents, nucleating agents, lubricants, plasticizers, fillers, reinforcing materials, pigments, dyes, flame retardants, antistatic agents and other additives May be added within a range that does not impair.

The order and method of mixing and melt-kneading the raw material polypropylene resin, isoprene monomer, radical polymerization initiator and other added materials are not particularly limited. For example, raw material polypropylene resin, isoprene monomer. Alternatively, the radical polymerization initiator and other additive materials added as necessary may be mixed and then melt-kneaded, or the raw material polypropylene resin, the radical polymerization initiator and other additive materials added as necessary. May be melt-kneaded after melt-kneading, and after obtaining the modified polypropylene resin by the above method, melt-kneading with additives and other resins added as necessary. Alternatively, part of the raw material polypropylene resin may be modified to form a masterbatch, and the remaining raw material polypropylene Len based resin may be melt-kneaded.
The melt-kneading may be repeated a plurality of times in order to mix the respective materials sufficiently uniformly.

The heating temperature at the time of melt-kneading varies depending on the type of resin and the like, but is usually 130 to 280 ° C.
It is preferable because the raw material polypropylene resin is sufficiently melted and is not thermally decomposed, and sufficient foamability can be obtained. The melt-kneading time (time after mixing the radical polymerization initiator and the isoprene monomer) is generally 30 seconds to 60 minutes.

As the melt-kneading device, for example, a kneader, a Banbury mixer, a Brabender, a kneading machine such as a single-screw extruder, a twin-screw extruder, a twin-screw surface renewing machine, a horizontal agitator such as a two-screw multi-disc device. An example is a device capable of heating a polymeric material such as a vertical stirrer such as a double helical ribbon stirrer to an appropriate temperature and kneading while applying an appropriate shear stress. Of these, a single-screw or twin-screw extruder is particularly preferable from the viewpoint of productivity.

As described above, the modified polypropylene resin preferably used in the present invention can be obtained.

The polypropylene resin foamed sheet of the present invention is prepared by melt-kneading a polypropylene resin and a foaming agent in an extruder, adjusting the foaming temperature in the extruder, and using a specific circular die having an annular slit. A cylindrical foam is obtained by extruding it into the atmospheric pressure from the slit of the die, and then while taking the obtained cylindrical foam, it is stretched and cooled by a molding process with a cooling cylinder (mandrel), then cut open and cut into a sheet. It is easily manufactured by the method. Further, extrusion foaming may be performed continuously with the production of the polypropylene resin.

As described above, the specific circular die is an inner cylinder directly supporting the inner portion (inner cylinder portion) of the annular slit of the circular die, which is directly connected to the outer cylinder portion that divides the polypropylene resin flow path. Part support structure 30
It is a circular die having more than 40, more than 40, and usually less than 80. Resin is extruded from the annular slit of such a circular die to produce a foam, and then a foam sheet, such as the foam sheet of the present invention, for example, when heat-molded into a molding container, with the maximum value of the side thickness. It is possible to manufacture a high quality molded container having a difference from the minimum value of 0.5 mm or less.

As the foaming agent, aliphatic hydrocarbons,
Alicyclic hydrocarbons, halogenated hydrocarbons, inorganic gas,
For example, water. These may be used alone, or 2
You may use it in combination of 2 or more types.

The addition amount (kneading amount) of the foaming agent varies depending on the type of the foaming agent and the target expansion ratio, but is 0.5 to 10 parts per 100 parts of the polypropylene resin. Of 0.1 to 0.5 g / cc is preferable from the viewpoint that a foamed sheet having good heat insulation and good rigidity can be obtained.

If necessary, a nucleating agent such as sodium bicarbonate-citric acid or talc may be used in combination to control the bubble diameter of the obtained foamed sheet to an appropriate size. The amount of the nucleating agent used, if necessary, is usually preferably 0.01 to 3 parts with respect to 100 parts of the polypropylene resin.

Further, when manufacturing the foamed sheet,
You may use together a thermoplastic resin in the range which does not impair the foamability of polypropylene-type resin.

The polypropylene-based resin foamed sheet of the present invention thus obtained is generally heat-molded to fill foods such as a container for bento, a container for pasta, a container for prepared foods, a container for instant noodles and the like. It can be molded into a molded article for that purpose, and can be suitably used for applications such as cooking in a microwave oven and reheating.

Examples of the heat molding include plug molding, matched mold molding, straight molding, drape molding, plug assist molding, plug assist reverse draw molding, air slip molding, snapback molding, reverse draw molding, and the like. Examples include free drawing molding, plug and ridge molding, and ridge molding.

When the molded product is a molded container, the difference between the maximum value and the minimum value of the thickness of the side portion of the container can be 0.5 mm or less, further 0.3 mm or less. When the difference between the maximum value and the minimum value of the thickness of the side portion of the container is too large, the appearance and rigidity of the molded container tend to be poor.

As described above, the polypropylene-based resin foam sheet of the present invention may be directly subjected to heat molding, but a polypropylene-based resin non-foamed layer may be laminated to improve rigidity, appearance and moldability. Good.

The polypropylene resin used as the base resin for the polypropylene resin non-foamed layer is as follows:
The polypropylene resin can be used. Among them, general polypropylene resins that have been conventionally used are preferable in terms of cost and processability.

Examples of the conventional polypropylene resins conventionally used include propylene homopolymers, block copolymers of propylene and other monomers (eg ethylene, butene 1 etc.), random copolymers. And crystalline polymers such as These may be used alone or in combination of two or more.

The thickness of the polypropylene resin non-foamed layer is, for example, 10 to 120 μm, more preferably 15 to 120 μm.
The thickness is preferably 80 μm from the viewpoint of easy lamination by thermal lamination.

The polypropylene resin non-foamed layer contains:
If necessary, antioxidants, metal deactivators, phosphorus-based processing stabilizers, UV absorbers, UV stabilizers, optical brighteners, metal soaps, stabilizers such as antacid adsorbents, crosslinking agents, chain transfer Agent,
Nucleating agents, lubricants, plasticizers, fillers, reinforcing materials, pigments, dyes,
You may add additives, such as a flame retardant and an antistatic agent.

The method for producing the non-foamed polypropylene resin layer is not particularly limited, but C which is generally used is used.
PP (unstretched polypropylene film) or OPP (biaxially stretched polypropylene film) can be used. These polypropylene resin films may be a laminated film having two layers or three or more layers as long as the effects of the present invention are not impaired.

The polypropylene-based resin laminated foamed sheet of the present invention, in which the polypropylene-based resin non-foamed layer is laminated on the polypropylene-based resin foamed sheet, may be further printed.

The printing is carried out with a printing ink containing a mixture of a printing ink resin, a solvent and a pigment as a main component.

An anchor coat agent, an antistatic agent, a stabilizer, an antioxidant, a dispersant and the like may be added to the printing ink as required. However, the printing is not limited to the above, as long as the object of the present invention can be achieved.

Examples of the resin for the printing ink include a copolymer of vinyl chloride and vinyl acetate, a chlorinated product of rubber, a chlorinated product of polypropylene (PP), a polymer of acrylic acid and its derivative, dimer acid and polyamine. Examples of the condensate, a polymer of polyester or polyether and diisocyanate, and a cell source nitrate ester compound. These may be used alone or in combination of two or more. Particularly, chlorinated polypropylene is preferable from the viewpoint of adhesiveness with polypropylene resin.

The printing is performed by a known method such as gravure printing. There is no particular limitation on the pattern of printing, etc., by arranging the printing between the polypropylene resin non-foamed layer and the polypropylene resin foamed sheet, it is possible to obtain a foamed laminated sheet having gloss and excellent design, Further, a foam laminate is obtained.

Examples of the method for producing the polypropylene resin foamed laminated sheet of the present invention include an extrusion lamination method, a thermal lamination method, and a method of laminating a non-foamed layer via an adhesive. In particular, a film made of polypropylene resin is superposed on a foamed sheet, and is fed out, and sandwiched by a temperature-controlled heat roll, and at the same time, thermal lamination in which pressure bonding is performed is preferable, which is preferable.

Since the polypropylene-based resin laminated foam sheet of the present invention is excellent in hot moldability such as plug molding, vacuum molding, and pressure molding, it is possible to obtain a molded product having a small thickness unevenness and a beautiful appearance.

Examples of the heat molding are the same as in the case of the polypropylene resin foam sheet of the present invention, that is, plug molding, matched mold molding, straight molding,
Drape molding, plug assist molding, plug assist
Examples thereof include a reverse draw molding, an air slip molding, a snapback molding, a reverse draw molding, a free drawing molding, a plug and ridge molding, and a ridge molding.

The polypropylene-based resin laminated foam sheet of the present invention can also be molded by heating to a molded article similar to that of the polypropylene-based resin foam sheet of the present invention, and can be suitably used for the same application. When the molded product is a molded container, the difference between the maximum value and the minimum value of the thickness of the container side can be 0.5 mm or less, further 0.3 mm or less, and the effect in that case is also the same. Is.

[0077]

EXAMPLES Next, the present invention will be explained based on examples, but the present invention is not limited to these examples.

First, the evaluation method used below will be described.

(Density of Foamed Sheet) JIS-K6767
It measured according to.

(Closed Cell Rate of Foamed Sheet) ASTM D
It was measured by an air pycnometer according to the method described in 2856.

(Thickness of Foamed Sheet and Period of Thinned Section)
It was measured by the method described above.

(Number of Bubbles in Foamed Sheet) The number was measured by the method described above.

(Adhesiveness of Laminated Foamed Sheet) The obtained foamed laminated sheet was cut into 540 × 540 mm square and the inner size was 5
It was fixed to a frame of 00 × 500 mm, inserted into a heating furnace whose atmospheric temperature was adjusted to 200 ° C. for 30 seconds, and then taken out.
The film layer of the obtained foamed laminated sheet after heating was observed and evaluated according to the following criteria. B: No swelling of the film layer is observed. X: Blistering of the film layer is recognized.

(Formed Product of Foamed Sheet and Laminated Foamed Sheet) The obtained foamed sheet or laminated foamed sheet was 640
After being cut out into a 640 mm square and fixed to a frame having an inner size of 600 × 600 mm, it was introduced into a heating furnace whose temperature was adjusted to 200 ° C. and heated for 30 seconds. Immediately after heating, it is molded in a mold whose temperature is adjusted to 60 ° C and molded into a molding container (diameter 150 mm
X bottom diameter 120 mm x depth 20 mm) was obtained. At that time, the mold used was a mold in which 2 × 2 molds for molding the above-mentioned shape were arranged, and four molded bodies were obtained at one time. The maximum value and the minimum value of the thickness of the side portion of the container were measured for each of the obtained four molded products. The measurement was performed by cutting out the container side from the obtained container and measuring the center of the container side (the midpoint between the mouth and bottom of the container) at 5 mm intervals in the container circumferential direction using a thickness gauge. The difference between the maximum value and the minimum value was calculated and evaluated according to the following criteria. ⊚: The difference between the maximum thickness and the minimum thickness of the side portions is 0.3 mm or less in all the molded products. ◯: The difference between the maximum thickness and the minimum thickness of the side portions is 0.5 mm or less in all the molded products. Δ: The difference between the maximum thickness and the minimum thickness of the side portion of the molded body is 0.5 m
One or two of the four or more m are recognized. X: The difference between the maximum thickness and the minimum thickness of the side portion of the molded body is 0.5 m
3 to 4 of 4 or more are recognized.

Example 1 Propylene homopolymer (J10 manufactured by Grand Polymer Co., Ltd.)
3) 100 parts and 0.3 parts of radical polymerization initiator (t-butylperoxyisopropyl monocarbonate) were stirred and mixed with a ribbon blender, and the mixture was fed to a twin-screw extruder with a metering feeder, and a liquid addition pump was used. 0.5 parts of isoprene was supplied from the middle of the extruder, melt-kneaded in the twin-screw extruder, and melt-extruded to obtain modified polypropylene resin pellets.

The twin-screw extruder was of the same-direction twin-screw type, and had a screw diameter of 44 mmφ and a maximum screw effective length (L / D) of 38. Set the temperature of the cylinder part of this twin-screw extruder to 1 before pressing the isoprene monomer.
The temperature was set to 80 ° C., 200 ° C. after the pressurization of isoprene, and the screw rotation speed was set to 150 rpm.

100 parts of the modified polypropylene resin,
A blend of 0.05 part of blended oil and 0.5 part of cell nucleating agent (Cerbon SC / K manufactured by Eiwa Kogyo Co., Ltd.) was stirred and mixed with a ribbon blender, and the mixture was fed to a 90-125 mmφ tandem type extruder, and 200 After being melted in the first stage extruder (90 mmφ) set to ℃, 1.6 parts of isobutane as a foaming agent was press-mixed with 100 parts of the modified polypropylene resin, and 165 ° C. Second set to (measured by a temperature sensor installed in the room)
It is cooled in a multi-stage extruder (125 mmφ) and discharged from a circular die (120 mmφ) under atmospheric pressure.
mm, the length of the main body is 800 mm, while drawing it at 4.6 m / min while drawing and cooling it to obtain a cylindrical foam, which is cut with a cutter to form 10
A foamed sheet having a width of 00 mm was obtained. The circular die used at that time was one in which the number of inner cylindrical supporting structure portions that divide the resin flow path and which were directly coupled to the outer cylindrical portion was 36.

Next, the foamed sheet is moved at a speed of 12 m / min.
The thickness is 25μ on a heated roll that is heated to 200 ℃.
m of unstretched polypropylene-based resin film was superposed and supplied, and after laminating the films, the film was cooled with a roll whose temperature was adjusted to 30 ° C. and wound up to obtain a laminated foam sheet.

Table 1 shows the properties of the obtained foamed sheet.

Further, the adhesiveness of the obtained foamed sheet and the molded product of the laminated foamed sheet and the laminated foamed sheet was evaluated. The results are shown in Table 2.

Example 2 The number of inner cylinder supporting structure parts which divide the resin flow path of the circular die used and which are directly coupled to the outer cylinder part is 45.
A foamed sheet was obtained in the same manner as in Example 1 except that the location was set. Then, a laminated foam sheet was obtained in the same manner as in Example 1.

Table 1 shows the properties of the obtained foamed sheet.

Further, the adhesiveness of the obtained foamed sheet and the molded product of the laminated foamed sheet and the laminated foamed sheet was evaluated. The results are shown in Table 2.

Comparative Example 1 Of the inner cylindrical portion supporting structure portion that divides the resin flow path of the circular die used, the number of those directly coupled to the outer cylindrical portion is 12.
A foamed sheet was produced in the same manner as in Example 1 except that the locations were set. Then, a laminated foam sheet was obtained in the same manner as in Example 1.

The characteristics of the foamed sheet thus obtained are shown in Table 1.

Further, the adhesiveness of the obtained foamed sheet and the molded product of the laminated foamed sheet and the laminated foamed sheet was evaluated. The results are shown in Table 2.

Comparative Example 2 0.3 part of the bubble nucleating agent was added, and the number of inner cylinder supporting structure parts that divide the resin flow path of the circular die used were directly bonded to the outer cylinder part at 12 positions. Except that
A foamed sheet was obtained in the same manner as in Example 1. Then, a laminated foam sheet was obtained in the same manner as in Example 1.

The characteristics of the foamed sheet thus obtained are shown in Table 1.

Further, the adhesiveness of the obtained foamed sheet and the molded product of the laminated foamed sheet and the laminated foamed sheet was evaluated. The results are shown in Table 2.

Comparative Example 3 Example 1 except that the amount of the bubble nucleating agent added was 0.3 part.
A foamed sheet was obtained in the same manner as. Then, a laminated foam sheet was obtained in the same manner as in Example 1.

The properties of the resulting foamed sheet are shown in Table 1.

Further, the molded articles of the obtained foamed sheet and laminated foamed sheet and the adhesiveness of the laminated foamed sheet were evaluated. The results are shown in Table 2.

[0103]

[Table 1]

[0104]

[Table 2]

From the results of Table 1 and Table 2, the number of bubbles in the foamed sheet and the number of cycles of the thin portion are 30 cells / mm ² or more,
It can be seen that a molded body with less uneven thickness can be obtained by setting the rate to 30 times / m or more. It is also understood that, in the case of a laminated foam sheet in which film layers are similarly laminated, it is possible to obtain a laminated foam sheet having a good moldability without swelling of the film during molding and heating.

[0106]

EFFECTS OF THE INVENTION The polypropylene resin foamed sheet of the present invention, when the number of cycles of the thin portion is set to 30 times / m or more, makes it possible to obtain a good molded product having less thickness unevenness when heat-molded. At the same time, the number of bubbles is 30 /
When the thickness is ² mm ² or more, a polypropylene-based resin laminated foam sheet having good moldability without swelling of the film during molding and heating can be obtained even in the laminated foam sheet obtained by laminating films.

Further, in the case of the polypropylene resin laminated foam sheet of the present invention, by laminating the polypropylene resin which is the same resin as the foam sheet, the recyclability and the appearance are excellent.

The polypropylene-based resin foamed sheet and the polypropylene-based resin laminated foamed sheet of the present invention have excellent heat resistance and oil resistance by using a polypropylene-based resin as the base resin, and are provided with a foamed layer. Therefore, it is excellent in heat insulation and lightweight.

From the above, the polypropylene-based resin foamed sheet of the present invention is excellent in moldability and secondary workability, and by using the foamed sheet, a polypropylene-based resin laminated foamed sheet having good moldability can be obtained. The molded container obtained by heat-molding these sheets has a beautiful appearance and is excellent in heat resistance, oil resistance, light weight, heat insulation, and moldability. It can be suitably used for a food container for heating in a microwave oven.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a result obtained by measuring a relationship between a width direction and a thickness of a foamed sheet.

FIG. 2 is a schematic cross-sectional explanatory view showing an example of an inner cylindrical portion support structure portion in a circular die.

FIG. 3 is a schematic cross-sectional explanatory view showing a cross section taken along the line AA in FIG.

[Explanation of symbols]

1 Inner tube 2 annular slit 3 Resin flow direction 4 resin flow path 5 Inner tube support structure 6 Resin flow path dividing part (12 places) 7 Outer cylinder

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) B29L 7:00 B29L 7:00 22:00 22:00 F term (reference) 3E033 AA08 BA16 BB08 CA07 CA09 FA04 4F100 AK07A AK07B AK07C AL06A BA02 BA03 BA06 BA07 BA10A BA10B BA10C BA13 CA01A CA02A DJ01A EJ17 EJ42 GB16 JA13A YY00A 4F207 AA11 AB02 AB03 AG01 AG03 AG20 AH54 KA01 KA11 KL62

Claims (6)

[Claims] 1. An average thickness of 1 to 5 mm, a value obtained by dividing the difference between the maximum value and the minimum value of the thickness by the average thickness is 0.20 or less, the closed cell ratio is 60% or more, and the density is 0. 1-0.5g / cc
Of the polypropylene resin foam sheet, wherein the number of bubbles per unit area is 30 cells / mm ² or more, and the number of cycles of the periodic thin portion seen in the width direction of the sheet is 30 times / m.
The polypropylene-based resin foamed sheet according to the above. 2. The polypropylene-based resin foam according to claim 1, wherein the base resin of the polypropylene-based resin foamed sheet is a modified polypropylene-based resin obtained by melt-kneading a raw material polypropylene-based resin, isoprene and a radical polymerization initiator. Sheet. 3. A polypropylene resin laminated foam sheet, wherein a polypropylene resin non-foamed layer is laminated on at least one surface of the polypropylene resin foam sheet according to claim 1. 4. A molded container obtained by heat-molding the polypropylene-based resin foam sheet according to claim 1, wherein the difference between the maximum value and the minimum value of the lateral thickness is 0.5 mm or less. Molded container characterized by. 5. A molded container obtained by thermoforming the polypropylene-based resin laminated foam sheet according to claim 3,
A molded container, wherein the difference between the maximum value and the minimum value of the side thickness is 0.5 mm or less. 6. A polypropylene-based resin that supports an inner portion (inner tube portion) of an annular slit of a circular die when a foamed sheet is extruded and a polypropylene-based resin foamed sheet is manufactured using a circular die having an annular slit. A circular die having 30 or more in the circumferential direction of the circular die, one of the inner tubular portion support structure portions that divides the flow path of (1) is directly coupled to a portion outside the annular slit (outer tubular portion), The method for producing a polypropylene-based resin foam sheet according to claim 1.