JP2005105210A - Polypropylene-based resin foamed sheet, method for producing the same and foamed molded article - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polypropylene-based resin foamed sheet excellent in secondary processes such as a heat-forming, etc., heat resistance, light weight, oil resistance, rigidity, etc., a polypropylene-based resin-laminated foamed sheet obtained by forming a non-foamed layer on the sheet, and a polypropylene-based resin foamed molded article obtained by heat-forming these sheets without forming an extreme thin thickness part at the side part, etc., of a container and excellent in heat resistance, light weight, oil resistance and rigidity. <P>SOLUTION: This extruded foamed sheet using the polypropylene resin as a base resin is characterized by having 0.1-0.3 g/cc density, 1-5 mm thickness, ≥60 % isolated cell ratio and ≤0.3 mm straightness. The polypropylene-based resin-laminated foamed sheet obtained by forming the non-foamed layer consisting of a polypropylene-base resin on at least one side surface of it and having ≤0.3 mm straightness, the method for producing the foamed sheet, and the polypropylene-based resin foamed article obtained by heat-forming the sheet are also provided. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a polypropylene resin foam sheet and a polypropylene resin foam laminate sheet excellent in heat resistance, light weight, oil resistance, rigidity, etc. excellent in secondary processing such as thermoformability. By thermoforming the sheet, it can be suitably used for packaging materials such as food containers and cushioning materials, building materials, automobile members and the like.

  A foamed sheet made of a thermoplastic resin is generally lightweight, has good heat insulation and buffering against external stress, and can easily obtain a molded body by secondary heating molding such as vacuum molding. It is widely used in applications such as cushioning materials, food containers, heat insulating materials, and automotive parts, mainly polyethylene resins. However, polystyrene resin foam sheets widely used in food containers and the like have the disadvantage of being inferior in heat resistance and oil resistance due to the nature of the polystyrene resin as the base material.

  On the other hand, polypropylene-based resins are expected as next-generation foaming resins because they are excellent in heat resistance and oil resistance. Since it is extremely difficult to obtain foam by extrusion foaming with a linear polypropylene resin itself, in recent years, it is possible to obtain foam by extrusion foaming by introducing a branched structure into the polypropylene resin. Resin has been developed. Along with this, a technique for obtaining a foamed sheet by extruding and foaming a polypropylene resin is disclosed.

  A conventional extruded foam sheet made of a thermoplastic resin usually melts the resin with an extruder, kneads the obtained melt and foaming agent under high temperature and high pressure, and then passes the mixture through a circular die having an annular slit. It is produced by a method of producing a foam sheet by extruding it into a low pressure region and forming it with a cylindrical cooling cylinder.

  In the production of extruded foam sheets of polypropylene resin, the cylindrical resin extruded into the atmospheric pressure is expanded in the atmosphere through a circular die. A cylindrical foam having a long circumference is obtained. At that time, the extruded cylindrical foam is pushed out in a state of undulation in the circumferential direction. Such waviness of the foam is called a corrugate and appears as periodic thickness unevenness.

  The thickness unevenness caused by this corrugation is different in the corrugated valley and mountain of the corrugated, the degree of cooling due to the outside air temperature is different, and the foaming state after leaving the mold is different, so the thickness of the part where foaming is large becomes thick, This occurs because the thickness of the portion where foaming is small is reduced. In particular, when the expansion ratio of the foam is large, the corrugate tends to be large. In addition, when a resin having a low melt viscosity is used, the tendency is increased. In the case of a resin having a low melt viscosity, it is difficult to stretch at the time of stretch molding in a cooling cylinder after extrusion foaming, so that the corrugated stretch by stretching is small, and as a result, the thickness unevenness is thought to be large.

  Such uneven thickness due to the corrugate decreases the appearance and physical properties (thickness / smoothness, surface property) of the foam and may be unacceptable as a product. In particular, when a foam sheet is thermoformed to obtain a foam-molded container, uneven thickness of the foam sheet appears as uneven thickness of the foam-molded container, and an acceptable molded container is difficult to obtain.

  When thermoforming a foam sheet, the heated foam sheet is stretched and molded by a molding die. Of course, the stretched portion is thin. At that time, if there is a place where the thickness is thin, the stress applied at the time of molding concentrates on the thin portion, and the amount of stretching increases. As a result, the thickness reduction due to molding stretching becomes larger than other parts.

  In order to obtain a good foamed molded article, the present inventors have studied the molding of a foamed molded article using a foamed sheet manufactured so that the uneven thickness ratio of the foamed sheet is reduced in order to eliminate the thickness unevenness of the foamed sheet. Went. The uneven thickness ratio is a value obtained by gradually grading the difference between the maximum value and the minimum value of the thickness in the width direction of the foamed sheet by the average thickness. However, when the average thickness of the foamed sheet is increased, thickness unevenness may occur in the obtained molded product even though the uneven thickness ratio is small. In other words, even if the ratio of the difference between the maximum value and the minimum value of the thickness and the ratio of the average thickness is reduced, if the average thickness of the foam sheet is large, the difference between the maximum thickness and the minimum thickness is increased, and as a result, the molding obtained It was found that uneven thickness occurred in the body. In particular, it has been found that when the portion showing the maximum thickness and the portion showing the minimum thickness are close to each other, the thickness unevenness tends to occur in the molded body.

  As described above, the thickness unevenness of the foamed sheet may reduce not only the appearance of the foamed sheet but also the appearance and physical properties of the foamed molded article obtained by thermoforming.

  There is an invention in which the thickness unevenness of the foam sheet is defined (Patent Document 1). In this patent, a polypropylene resin foam sheet with little thickness unevenness is disclosed by defining the value of average minimum thickness / average maximum thickness. ing. However, when the portion showing the maximum thickness and the portion showing the minimum thickness are close, when such a foam sheet is formed, the portion showing the minimum thickness becomes extremely thin and an acceptable container may not be obtained. is there.

On the other hand, a value obtained by dividing the maximum value of the thickness of one cycle of the thickness by the minimum value is specified, and a method of reducing the thickness unevenness (Patent Document 2) or a method of reducing the thickness unevenness by coextrusion (Patent Document) 3) is disclosed. However, these methods require a facility for providing a sizing portion at the mold outlet or performing coextrusion. Such a method not only requires capital investment but also includes many technically difficult parts such as temperature control.
JP-A-5-338055 Patent 2003-165858 JP-2002-46164

  An object of the present inventor is to provide a polypropylene resin foam sheet excellent in secondary processability such as thermoforming in a polypropylene resin foam sheet and a method for producing the same. More specifically, a polypropylene resin foam sheet having good surface smoothness obtained by this production method, a laminated foam sheet obtained by laminating a non-foamed layer on the foam sheet, and a heat resistance obtained by molding those sheets. The object is to provide a molded article having excellent properties, rigidity, light weight, and oil resistance.

  As a result of intensive studies to solve such problems, the present inventors have made the foamed sheet smooth and reduced the thickness difference, not the ratio between the maximum thickness and the minimum thickness, so that there is no thin portion. It has been found that a sheet molded body can be obtained. As a measure to reduce the height difference, it is effective to rapidly cool the surface temperature of the foam below the crystallization temperature of the foam base resin when the cylindrical foam passes through the cooling cylinder. As a result, the present invention has been completed.

  That is, the present invention is an extruded foam sheet using a polypropylene-based resin as a base resin, and has a density of 0.1 to 0.3 g / cc, a thickness of 1 to 5 mm, an aeration rate of 60% or more, and a straightness of 0.3 mm or less. A polypropylene resin laminate foam formed by forming a non-foamed layer made of a polypropylene resin on at least one surface of the polypropylene resin foam sheet according to claim 1 and claim 1. Polypropylene resin laminated foam sheet with a foam layer surface straightness of 0.3 mm or less (Claim 2), after melt-kneading a polypropylene resin and a foaming agent in an extruder, and adjusting the foaming temperature in the extruder Then, using a circular die having an annular slit, extruded into the atmospheric pressure from the slit of the die to obtain a cylindrical foam, In the method in which the cylindrical foam is drawn and stretched and cooled by a forming process using a cooling cylinder, and then cut into a sheet, the surface temperature of the cylindrical foam is reduced when the foam passes through the cooling cylinder. 2. The PP according to claim 1, wherein a gas is blown toward the surface of the foam at a location equal to or higher than the crystallization temperature of the base resin, and the foam surface temperature is rapidly cooled below the crystallization temperature of the base resin. A polypropylene resin foam molded body obtained by thermoforming the polypropylene resin foam sheet according to claim 1 or the polypropylene resin laminate foam sheet according to claim 2 (claim). It relates to item 4).

  In the polypropylene resin foam sheet of the present invention, by defining the smoothness of the surface, it is possible to prevent the occurrence of extreme thinness of the molded product due to the uneven thickness of the foam sheet, which has been a problem in the past. As a result, a polypropylene resin molded article having excellent heat resistance, rigidity, light weight, and oil resistance can be obtained.

  As the polypropylene resin of the base resin used in the production of the foam sheet of the present invention, an electron beam is applied to a linear polypropylene resin (hereinafter, this polypropylene resin may also be referred to as “raw polypropylene resin”). A modified polypropylene resin obtained by melting and kneading a raw material polypropylene resin, an isoprene monomer, and a radical polymerization initiator is preferable in that it has excellent foamability. In particular, a modified polypropylene resin obtained by melting and kneading a raw material polypropylene resin, an isoprene monomer, and a radical polymerization initiator is preferable in terms of easy production.

  Examples of the raw material polypropylene resin include crystalline polymers such as a propylene homopolymer, a block copolymer of propylene and another monomer, or a random copolymer of propylene and another monomer. The polypropylene homopolymer is preferable from the viewpoint of high rigidity and low cost, and is a block copolymer of the propylene and other monomers from the viewpoint of high rigidity and impact resistance. It is preferable. When the raw material polypropylene resin is a block copolymer of propylene and another monomer or a random copolymer of propylene and another monomer, the high crystallinity and high rigidity characteristic of the polypropylene resin From the viewpoint of maintaining good chemical resistance, the propylene monomer component contained is preferably 75% by weight or more, and more preferably 90% by weight or more of the whole.

  In the raw material polypropylene resin, the other monomer copolymerizable with propylene is selected from the group of monomers consisting of ethylene, α-olefin, cyclic olefin, diene monomer and vinyl monomer. 1 type or 2 types or more of monomers are mention | raise | lifted. Of these monomers, ethylene or butene-1 is preferable because it is inexpensive.

  The molecular weight (weight average molecular weight) of the raw material polypropylene resin is preferably in the range of 50,000 to 2,000,000 from the viewpoint of industrial availability, and from the point of being inexpensive, it is 100,000 to 1,000,000. More preferably, it is within the range.

  You may add other resin or rubber | gum to the said raw material polypropylene resin in the range which does not impair the effect of this invention as needed. The amount of these other resins or rubbers added to the raw material polypropylene resin varies depending on the type of the resin or the type of rubber and may be within the range not impairing the effects of the present invention as described above. Usually, it is preferably about 25% by weight or less.

  The modified polypropylene resin may be produced by melt-kneading a polypropylene resin, an isoprene monomer, another vinyl monomer copolymerizable with the isoprene monomer, and a radical polymerization initiator.

  When isoprene monomer and other vinyl monomer copolymerizable with this isoprene monomer are used in combination, the amount of other vinyl monomer copolymerizable with isoprene monomer is The amount is preferably 100 parts by weight or less with respect to 100 parts by weight of the body, and more preferably 75 parts by weight or less on average. When the addition amount of the other vinyl monomer copolymerizable with the isoprene monomer exceeds the above range, the viscosity of the resulting modified polypropylene resin is remarkably lowered, and the foamability may be lowered.

  The addition amount of the isoprene monomer to be melt kneaded is preferably 0.1 to 20 parts by weight, more preferably 0.3 to 10 parts by weight with respect to 100 parts by weight of the raw material polypropylene resin. preferable. When the amount of the isoprene monomer is less than the above range, the foamability of the modified polypropylene resin may be reduced. On the other hand, when the amount exceeds the above range, heat resistance and rigidity, which are characteristics of the polypropylene resin, may be obtained. Etc. may be damaged.

  Examples of the radical polymerization initiator generally include peroxides and azo compounds. Examples of the radical polymerization initiator include one or more organic peroxides such as ketone peroxide, peroxyketal, hydroperoxide, dialkyl peroxide, diacyl peroxide, peroxydicarbonate, and peroxyester. can give. Of these, those having particularly high hydrogen abstraction ability are preferred.

  The addition amount of the radical polymerization initiator is within a range of 0.1 to 10 parts by weight with respect to 100 parts by weight of the raw material polypropylene resin from the viewpoint of good foamability of the modified polypropylene resin and an economical viewpoint. It is preferable that it exists in the range of 0.2-5 weight part.

  Furthermore, the raw material polypropylene resin may contain an antioxidant, a metal deactivator, a phosphorus processing stabilizer, an ultraviolet absorber, an ultraviolet stabilizer, a fluorescent brightener, a metal soap, an antacid adsorbent, etc., if necessary. Stabilizers or additives such as crosslinking agents, chain transfer agents, nucleating agents, lubricants, plasticizers, fillers, reinforcing materials, pigments, dyes, flame retardants, antistatic agents, and the like within a range that does not impair the effects of the present invention You may add in.

  The order and method of mixing and melt-kneading these raw material polypropylene resins, isoprene monomers, radical polymerization initiators and other added materials are not particularly limited. For example, raw material polypropylene resins, isoprene monomers , Radical polymerization initiator and other additive materials added as needed may be mixed and then melt-kneaded, or raw material polypropylene resin, radical polymerization initiator and other additive materials added as needed Isoprene monomer may be melt-kneaded after melt-kneading, or after obtaining a modified polypropylene resin by the above method, it may be melt-kneaded with additives and other resins added as necessary Good, and after modifying a part of the raw material polypropylene to make a master batch, the remaining raw material polypropylene tree And it may be melt-kneaded.

  The heating temperature at the time of melt-kneading varies depending on the type of resin, but it is usually 130 to 300 ° C. that the raw material polypropylene-based resin is sufficiently melted and does not thermally decompose to obtain sufficient foamability. It is preferable in that it can be performed. The time for melt kneading (the time after mixing the radical polymerization initiator and the isoprene monomer) is generally 30 seconds to 60 minutes.

The melt kneading apparatus includes a kneader, a Banbury mixer, a Brabender, a single-screw extruder, a twin-screw extruder, etc., a two-axis surface renewal machine, a horizontal agitator such as a two-shaft multi-disc apparatus, or the like. Examples thereof include an apparatus capable of heating a polymer 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. Among these, a single-screw or twin-screw extruder is particularly preferable from the viewpoint of productivity. Moreover, in order to mix each material sufficiently uniformly, the melt kneading may be repeated a plurality of times.
As described above, the modified polypropylene resin composition in the present invention can be obtained.

  The polypropylene resin of the present invention has an MFR of 0.1 to 4 g / 10 min, more preferably 0.3 to 2 g / 10 min. When the MFR is smaller than 0.1, the extrudability is lowered. When the MFR is larger than 4, when the obtained foamed sheet is heated, the sheet droops greatly, and wrinkles may occur during molding.

  The MFR of the polypropylene resin can be measured according to ASTM D-1238 using a Toyo Seiki melt indexer.

In addition, the foam sheet made of the polypropylene resin in the present invention is prepared by melt-kneading the polypropylene resin and the foaming agent in the extruder, then adjusting the foaming temperature in the extruder, and using a circular die having an annular slit. Easily manufactured by a method of extruding into the atmospheric pressure from the slit to obtain a cylindrical foam, then drawing and cooling the cylindrical foam, then drawing and cooling, and then cutting it into a sheet. Is done. Further, extrusion foaming may be performed continuously with the production of the modified polypropylene resin composition.
Examples of the blowing agent include aliphatic hydrocarbons, alicyclic hydrocarbons, halogenated hydrocarbons, inorganic gases, water, and the like. Moreover, you may use combining those 1 type (s) or 2 or more types.

  The addition amount (kneading amount) of the foaming agent varies depending on the type of foaming agent and the target foaming ratio, but may be in the range of 0.5 to 10 parts by weight with respect to 100 parts by weight of the polypropylene resin composition. preferable.

  Moreover, in order to control the bubble diameter of a foam sheet to a suitable magnitude | size, you may use together nucleating agents, such as a sodium bicarbonate-citric acid mixture or a talc, as needed. The amount of the nucleating agent used as necessary is usually preferably 0.01 to 3 parts by weight with respect to 100 parts by weight of the polypropylene resin composition.

  Further, in the production of the foam sheet, a thermoplastic resin may be mixed as long as the foamability of polypropylene is not impaired.

  Further, in the production of the foam sheet of the present invention, an antioxidant, a metal deactivator, a phosphorus processing stabilizer, an ultraviolet absorber, an ultraviolet stabilizer, a fluorescent brightener, a metal within a range not impairing the effects of the present invention. Stabilizers such as soap and antacid adsorbents, or additives such as crosslinking agents, chain transfer agents, lubricants, plasticizers, fillers, reinforcing materials, pigments, dyes, flame retardants, antistatic agents may be added. .

  The average thickness of the foamed sheet made of the polypropylene resin in the present invention is 1 to 5 mm, more preferably 1 to 3 mm. If it becomes smaller than 1 mm, it will be inferior to heat insulation, rigidity, and buffer property, and if it becomes larger than 5 mm, it will be inferior to moldability.

  The thickness of the foam sheet in the present invention can be measured as follows. Measurement points are provided at intervals of 50 mm in the width direction of the foam sheet. The thickness of the foam sheet at each measurement point is measured with a thickness gauge (for example, a thickness gauge manufactured by teclock). The arithmetic average of each measurement point is calculated and set as the average thickness of the foamed sheet.

  In the polypropylene resin foam sheet of the present invention, the closed cell ratio is 60% or more, preferably 70% or more, more preferably 80% or more. If it is less than 60%, the molded container obtained by heat molding may be inferior in rigidity.

  The closed cell ratio of the foam sheet in the present invention can be measured by an air pycnometer according to the method described in ASTM D-2856.

  The density of the polypropylene resin foam sheet in the present invention is 0.1 to 0.3 g / cc, preferably 0.13 to 0.3 g / cc. If it is less than 0.1 g / cc, the corrugation becomes large and it is difficult to obtain a smooth sheet. When it is larger than 0.3 g / cc, the heat insulating property is poor.

  The density of the foamed sheet of the present invention can be measured according to JIS-K6767.

  The number of cells in the thickness direction of the polypropylene resin foam sheet in the present invention is 5 / thickness or more, preferably 7 / thickness or more. If it is less than 5 / thickness, the heat insulating property may be inferior. The number of bubbles in the thickness direction is obtained by sampling the center of the width of the foam sheet, observing an electron micrograph of the cross section in the width direction, and counting the number of bubbles in a vertical line.

  The number of bubbles in the thickness direction of the foamed sheet in the present invention can be measured as follows. The foamed sheet is cut in the width direction, and measurement parts are provided at intervals of 50 mm in the width direction. The number of bubbles in the thickness direction in the cross section of each measurement unit is measured. After the measurement, the arithmetic average of the number of bubbles in each measurement unit is calculated and used as the number of bubbles.

  The straightness of the polypropylene foam sheet in the present invention is preferably 0.3 mm or less, preferably 0.25 mm or less. When the straightness is 0.3 mm or more, a thin part is formed in the molded body after thermoforming, which may be unacceptable as a product.

  Straightness can be measured as follows. First, a strip-like sheet is cut out in the width direction of the foamed sheet at a width of 50 mm, and then the sample is cut at a length of 105 mm. The straightness of the width direction of the surface which did not contact the cooling cylinder of each obtained sample is measured using a shape measuring device (Surfcom / Contour Record manufactured by Tokyo Seiki Co., Ltd.). The measurement conditions at that time were a measurement length of 100 mm, a measurement pitch of 0.05 mm, and a measurement speed of 1.5 mm / sec. This measuring device is a device that continuously measures the irregular shape of the surface and calculates the straightness from the measurement result according to JISB0621. For the straightness in the present invention, the value having the largest straightness among the measured values of the obtained samples was adopted as the straightness of the sheet.

  The following method is mentioned as a manufacturing method of the foam sheet whose straightness in this invention is 0.3 mm or less. After melt-kneading the polypropylene resin and foaming agent in the extruder, adjust the foaming temperature in the extruder and use a circular die with an annular slit, and extrude it into the atmospheric pressure from the slit of the die to form a cylindrical foam. The surface of the cylindrical foam is obtained when the foam passes through the cooling cylinder in a method in which the cylindrical foam is taken and then stretched and cooled by a forming process using a cooling cylinder, and then cut into a sheet. Gas is blown toward the foam surface at a location where the temperature is equal to or higher than the crystallization temperature of the base resin, and the foam surface temperature is rapidly cooled below the crystallization temperature of the base resin.

  In this way, by rapidly cooling the surface temperature of the foam to below the crystallization temperature of the base resin, the foaming of the part where the thickness is to be thickened is stopped, and the thickness difference between the thick part and the thin part is reduced, As a result, it is a method of reducing the unevenness of the sheet surface.

  In the method for producing a polypropylene resin foam sheet of the present invention, the gas is preferably blown onto the surface of a cylindrical foam 50 to 150 mm from the tip of the cooling cylinder. When the die is closer to the die than 50 mm from the tip of the cooling cylinder, the blown gas circulates in the vicinity of the slit of the circular die, that is, the location where the corrugation is greatly generated, and as a result, the cooling of the corrugated crest surface by the gas proceeds. Problems such as wrinkles due to shrinkage occur. In addition, when the diameter is larger than 150 mm, the foam is sufficiently expanded and the thickness unevenness caused by the corrugation cannot be suppressed, so that a foam sheet having a target straightness of 0.3 mm or less can be obtained. It becomes difficult.

  In the method for producing a polypropylene resin foam sheet of the present invention, gas is blown toward the foam surface at a location where the surface temperature of the cylindrical foam is equal to or higher than the crystallization temperature of the base resin, and the foam surface is used as the base material. It is characterized by quenching below the crystallization temperature of the resin. In the place below the crystallization temperature, the thickness unevenness of the foam has already occurred, and a foam sheet having a straightness of 0.3 mm or less may not be obtained even if gas is blown to the place below the crystallization temperature. Moreover, when it does not cool below the crystallization temperature of base resin, thickness nonuniformity cannot be suppressed and a foam sheet with a straightness of 0.3 mm or less may not be obtained similarly.

  The crystallization temperature in the present invention is a crystal that is shown when a polypropylene resin is heated from 40 ° C. to 210 ° C. at a rate of temperature increase of 10 ° C./min and then cooled to 40 ° C. at 10 ° C./min with a differential scanning calorimeter. The peak temperature was defined as the crystallization temperature in the relationship between the calorific value based on crystallization and the temperature.

  The temperature of the gas blown to the foam surface, the air volume, and the wind speed are not particularly limited as long as it is cooled to the crystallization temperature or lower as described above. preferable. In addition, examples of the gas to be blown include nitrogen and carbon dioxide, but air is preferable because it is easily available.

  It is preferable to apply the gas to the foam evenly around the cylindrical foam. If there is non-uniformity in how the gas is blown, thickness unevenness may occur in the resulting sheet, which may be unacceptable as a product.

  FIG. 1 shows an example in which air is blown in the cooling cylinder portion. As shown in FIG. 1, a foam l pushed out in a cylindrical shape from a circular die a having an annular slit is stretched, cooled and molded by a cooling cylinder e. At that time, the air sent from the air blowing pipe c from the slit of the outer air blowing device b installed so as to surround the periphery of the cooling cylinder at a position o at a distance 50 to 150 mm from the tip of the cooling cylinder e is cylindrically foamed Spray body l. A non-contact type thermometer n (THERMO-HUNTER PT-3LF manufactured by Optics) is installed on the die side and the anti-die side at the position where the air is blown, and the cylindrical foam surface temperature is measured. Then, the temperature of the air to be blown and the air volume are adjusted so that the surface temperature of the cylindrical foam is equal to or lower than the crystallization temperature of the base resin. Thereafter, the cylindrical foam l is cut by a foam slitting cutter f to obtain the polypropylene resin foam sheet m of the present invention.

The polypropylene resin foam laminated sheet of the present invention is characterized in that a polypropylene resin non-foamed layer is laminated on a polypropylene resin foam sheet. As the polypropylene resin used as the base resin of the polypropylene resin non-foamed layer, the above-mentioned polypropylene resin can be used. Among them, a conventional polypropylene resin used conventionally is preferable in terms of cost and processability. Examples of the polypropylene resin include crystalline polymers such as a propylene homopolymer, a block copolymer of propylene and another monomer, or a random copolymer of propylene and another monomer. Moreover, they can be used 1 type or in combination of 2 or more types, and a non-foamed layer may be 2 or more layers.
In the polypropylene resin non-foamed layer of the present invention, an antioxidant, a metal deactivator, a phosphorus processing stabilizer, an ultraviolet absorber, an ultraviolet stabilizer, a fluorescent whitening agent, a metal soap, an antacid adsorption as necessary. Stabilizers such as agents, or additives such as crosslinking agents, chain transfer agents, nucleating agents, lubricants, plasticizers, fillers, reinforcing materials, pigments, dyes, flame retardants and antistatic agents may be added.

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

  The polypropylene resin foam laminated sheet of the present invention may form a printing layer. Printing is performed with an ink whose main component is a mixture of resin, solvent, and pigment. Resins for printing inks include copolymers of vinyl chloride and vinyl acetate, chlorinated products of rubber, chlorinated products of PP, polymers of acrylic acid and its derivatives, condensates of dimer acid and polyamine, polyesters or polyethers Examples include a polymer of diisocyanate and a nitrate ester compound of cellulose. Moreover, you may use those resin 1 type or in mixture of 2 or more types. In particular, chlorinated polypropylene is preferable from the viewpoint of adhesiveness with a polypropylene resin. Moreover, you may add an anchor coating agent, an antistatic agent, a stabilizer, antioxidant, a dispersing agent, etc. to printing ink as needed. However, the printing layer is not limited to the above as long as the object of the present invention can be achieved.

The printing layer is formed by a known method such as gravure printing. The printing pattern is not particularly limited, and the foamed laminated sheet and the foamed laminate having gloss and excellent design properties can be obtained by disposing the printed layer on the inner surface (the foamed layer side of the polypropylene resin layer).
Examples of the method for producing the polypropylene resin foam laminated sheet of the present invention include an extrusion lamination method, a thermal lamination method, a coextrusion method, and a method of laminating a non-foamed layer via an adhesive. Among these, the extrusion lamination method and the thermal lamination are preferable from the viewpoint of easy lamination.

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

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

Next, production methods and foams according to the present invention will be described based on Examples and Comparative Examples, but the present invention is not limited to only the Examples.
(Formability evaluation)
A single-molding machine for foam sheets (VAS-66-45T manufactured by Toko Co., Ltd.) was used, and a rectangular container having a container size of 210 mm × 180 mm × H30 mm was used as the molding die. For the molding, matched mold molding (mold clearance 1.5 mm) was performed using the upper mold as a female mold and the lower mold as a male mold. Ten molded bodies were molded, and the molded bodies were evaluated according to the following criteria.
◯: There are no extremely thin portions (thin portions) on the container side portions of all the molded products. Δ: Among 10 pieces, thin portions are recognized on the container side portions of 1 to 5 molded products. A thin part is recognized by the container side part of 6-10 molded bodies among 10 (use main auxiliary material)
The following resins and films were used in Examples and Comparative Examples.

Resin A: 100 parts by weight of propylene homopolymer (Sumitomo Mitsui Polyolefin J103WB, MFR 3 g / 10 min) is blended with 0.29 parts by weight of t-butyl peroxybenzoate as a radical generator, and a ribbon blender is used. For 5 minutes. This mixture was made into a twin screw extruder (TEX44) manufactured by Nippon Steel Co., Ltd. (the twin screw extruder is the same direction twin screw type, the hole diameter of the cylinder is 44 mmφ, and the maximum screw effective length (L / D) was 38.) was fed from the hopper at a feed rate of 50 kg / h, and isoprene monomer was fed at a rate of 0.25 Kg / h from the introduction part provided in the middle using a metering pump (propylene homopolymer). A modified polypropylene-based resin (MFR 0.5 g / 10 min, crystallization temperature 127 ° C.) obtained by supplying water at a ratio of 0.5 parts by weight with respect to 100 parts by weight, and cooling the strands with water.
Resin B: Propylene homopolymer (J103WB manufactured by Sumitomo Mitsui Polyolefin Co., Ltd., MFR 3 g / 10 min)
Nucleator C: Serbon SC / K manufactured by Eiwa Kogyo Co., Ltd.
Film D: Tonen Co., Ltd. unstretched polypropylene film 25 μm

(Example 1)
A compound obtained by stirring and mixing the resin A and the nucleating agent C with a ribbon blender at a compounding ratio of 100: 1.1 was supplied to a tandem extruder composed of a 90 mmφ uniaxial-125 mmφ uniaxial and set to 220 ° C. After being melted in the first stage extruder (90 mmφ), 100 parts by weight of the above resin composition was mixed with isorich butane (manufactured by Mitsui Chemicals, Inc., 85 parts by weight of isobutane, 15 parts by weight of normal butane) as a blowing agent. 1.6 parts by weight with respect to the mixture, cooled in a second stage extruder (125 mmφ) set at 160 ° C., and discharged from a circular die (127 mmφ) at a discharge rate of 80 kg / hr under atmospheric pressure. A foamed sheet having a width of 1050 mm was obtained by cutting with a cutter while taking up at 4.4 m / min while being molded with a 336 mm cooling cylinder.

At that time, air adjusted to 33 ° C. was blown at a flow rate of 5 Nm ³ / min from an outer air blowing device having a slit of 2 mm in the circumferential direction of the cooling cylinder at a location 60 mm from the tip of the cooling cylinder. At that time, the foam surface temperature just before spraying and the foam surface temperature just after spraying were measured. Table 1 shows the measured foam surface temperature, physical properties of the obtained foamed sheet, and molded body evaluation.
(Example 2)
A foamed sheet was obtained in the same manner as in Example 1 except that the amount of air blown was ³ Nm ³ / min. Table 1 shows the measured foam surface temperature, foam sheet physical properties and molding evaluation.
(Example 3)
A foam sheet was obtained in the same manner as in Example 1 except that the position of the outside air blowing device was set to 120 mm from the tip of the cooling cylinder. Table 1 shows the measured foam surface temperature, foam sheet physical properties and molding evaluation.
Example 4
The foamed sheet obtained in Example 1 was drawn out and introduced into a cooling roll, and the resin B was extruded from the T die into a film at a resin temperature of 250 ° C., and dripped down to a thickness of 45 μm between the cooling roll and the foamed sheet. . At the same time, the film D was introduced between the resin B and the cooling roll and pressure-bonded to obtain a foamed laminated sheet comprising a foamed sheet, a non-foamed layer and a film. At that time, the formation of the non-foamed layer was made to be a surface that did not contact the cooling cylinder of the foamed sheet.

(Comparative Example 1)
A foam sheet was obtained in the same manner as in Example 1 except that the position of the outer air blowing device described here was set to 200 mm from the tip of the cooling cylinder. Table 1 shows the measured foam surface temperature, foam sheet physical properties and molding evaluation.

(Comparative Example 2)
A foamed sheet was obtained by the method described in Example 1 except that the air volume of air to be blown from here was 1 Nm ³ / min. Table 1 shows the measured foam surface temperature, foam sheet physical properties and molding evaluation.
(Comparative Example 3)
A foamed sheet was obtained by the method described in Comparative Example 1. Next, a foamed laminated sheet was obtained by the method described in Example 4. Table 1 shows the measured foam surface temperature, foam sheet physical properties and molding evaluation.

Schematic diagram around the cooling cylinder in the manufacturing process of extruded foam sheets

Explanation of symbols

a Circular die b Outside air spraying device e Cooling cylinder k Foam sheet l Tubular foam n Non-contact thermometer

Claims (4)

It is an extruded foam sheet using a polypropylene resin as a base resin, and has a density of 0.1 to 0.3 g / cc, a thickness of 1 to 5 mm, an aeration rate of 60% or more, and a straightness of 0.3 mm or less. A polypropylene resin foam sheet. A polypropylene resin laminated foam sheet in which a non-foamed layer made of a polypropylene resin is formed on at least one surface of the polypropylene resin foam sheet according to claim 1, wherein the straightness of the foam layer surface is 0.3 mm or less. -Based resin laminated foam sheet. After melt-kneading the polypropylene resin and foaming agent in the extruder, adjust the foaming temperature in the extruder and use a circular die with an annular slit, and extrude it into the atmospheric pressure from the slit of the die to form a cylindrical foam. The surface of the cylindrical foam is obtained when the foam passes through the cooling cylinder in a method in which the cylindrical foam is taken and then stretched and cooled by a forming process using a cooling cylinder, and then cut into a sheet. 2. The foam surface temperature is rapidly cooled below the crystallization temperature of the base resin by blowing a gas toward the foam surface at a location where the temperature is equal to or higher than the crystallization temperature of the base resin. Of PP resin foam sheet. A polypropylene resin foam molded article obtained by thermoforming the polypropylene resin foam sheet according to claim 1 or the polypropylene resin laminated foam sheet according to claim 2.

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