JP2949046B2 - Polypropylene resin foam laminate sheet and base material for molding automotive ceiling materials - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated sheet of a polypropylene resin foam and a sheet for molding an automobile ceiling material.

[0002]

2. Description of the Related Art Conventionally, an elongated foam or
As a foam sheet for molding used to mold various containers, automotive ceiling materials, door interior materials, trunk room members, etc., a thermoplastic resin is melt-kneaded with a foaming agent in an extruder and then pressed under low pressure. BACKGROUND ART Foam sheets obtained by so-called extrusion foaming, which are foamed by being discharged, are widely used.

[0003] In such an extrusion foaming method, when a melt-kneaded product of a thermoplastic resin and a foaming agent is extruded under low pressure from an extruder, foaming is caused by expansion of the foaming agent in the melt-kneaded material. However, if the temperature of the resin is increased, the viscosity drops sharply, the resin cannot retain the foaming agent, and escapes from the resin to form an open-cell foamed sheet. Conversely, the resin temperature increases to increase the viscosity of the resin. When the resin is lowered, the crystallization of the resin proceeds, and as a result, there is a problem that the foam does not foam sufficiently and uniformly and the foam sheet surface becomes uneven, so that the foam is sufficiently uniformly foamed and the foaming agent is used. It is necessary to perform extrusion foaming at a temperature at which the resin has viscoelasticity that can be retained in the resin. The temperature range in which viscoelasticity suitable for extrusion foaming is obtained differs depending on the type of resin, and this temperature range is generally referred to as a foaming suitable temperature range.

However, in a propylene-based resin having a relatively high crystallinity, the viscoelasticity of the resin is greatly changed by a slight temperature change, and the temperature range for foaming is very narrow. It is very difficult to carry out extrusion foaming while maintaining the resin temperature within such a narrow temperature range, and when the extrusion foaming temperature fluctuates and deviates from the suitable foaming temperature range, the foamed portion has an open-cell structure. And the surface became uneven, and it was difficult to obtain a foamed sheet having good overall and uniform properties. Conventionally, in the case of a non-crosslinked propylene-based resin, a relatively good foamed sheet can be obtained only at a low expansion ratio of density exceeding 0.2 g / cm ³ or at a density of 0.013 g / cm ^3. And a high expansion ratio of less.

[0005] The above-mentioned problems are considered to be caused by the high crystallinity of the propylene-based resin, and the density of the propylene-based resin is not higher than 0.
The reason why a foam sheet having a low expansion ratio of more than 2 g / cm ³ can be obtained relatively favorably is that the resin temperature at the time of extrusion foaming is higher than the crystallization temperature of the resin because the ratio of the resin is larger than the amount of the foaming agent. Is also considered to be due to the fact that it can be set to a considerably higher temperature. The density is 0.013 g / c.
The reason why a foam sheet having a high expansion ratio of less than m ³ can be obtained relatively favorably is as follows.

In general, a foaming olefin-based resin in the process of extrusion foaming is subjected to a cooling operation from the outside by using a cooling means, thereby solidifying the cell walls to obtain a good foamed sheet. However, since the propylene-based resin has a higher degree of crystallinity than low-density polyethylene, the calorific value during crystallization is large. This heat hinders the cooling and thus the solidification of the cell walls, and breaks or deforms the cells of the propylene-based resin in the process of foaming.

Therefore, by foaming a large amount of a foaming agent, the temperature of the propylene-based resin in the course of foaming is rapidly lowered by utilizing the heat of vaporization (heat of expansion) of the foaming agent, thereby solidifying the cell wall. Promote. Further, a large amount of the foaming agent has a function of delaying crystallization of the resin in the extruder. As a result, a relatively good foam sheet can be obtained. However, in this case, the foamed sheet to be obtained necessarily has a density of 0.013 g / cm ³ because of the necessity of blending a large amount of a foaming agent.
High expansion ratio of less than Also in this case, the suitable foaming temperature range is only about 0.6 ° C.

In view of the fact that only non-crosslinked propylene-based resins have produced only extruded foams having a high expansion ratio or a low expansion ratio as described above, the applicant of the present invention has a density of 0.
An extruded non-crosslinked propylene resin foam in the range of 2 to 0.013 g / cm ³ and each having specific physical properties has already been found (JP-A-4-363).
227, JP-A-5-98058, JP-A-5-98058
-124125, JP-A-5-230255).

[0009]

However, although these foams sufficiently solve the problems each has, they usually have a flat structure whose cell structure is short in the thickness direction (specifically, the foam When the average cell diameter in the thickness direction is a, the average cell diameter in the width direction is b, and the average cell diameter in the extrusion direction is c, in the portion excluding the vicinity of the surface layer, the cell diameter in the width direction with respect to the cell diameter a in the thickness direction Each ratio of the average cell diameter b and the average cell diameter c in the extrusion direction is a / b =
(Approximately 0.35, a / c = 0.32)), so that sufficient cushioning properties cannot be obtained, and when used as a packaging container for packaging a relatively heavy one. Had a problem with the strength of the body, and still had problems to be solved.

[0010] In order to improve the compressive strength of the foam sheet and to solve such a problem, it is conceivable to increase the thickness of the foam sheet.
Although the base resin used to obtain a non-crosslinked propylene resin extruded foam in the range of 0.013 g / cm ³ is superior in extrusion foamability to the propylene resin used before, However, since the melt viscosity in the extruder is low, the pressure at the mouth of the extruder also becomes low. In order to obtain a good foam, the pressure at the mouth of the extruder must be increased. For this purpose, it is necessary to set the discharge gap of the resin discharge port of the base portion to be narrow, and if the discharge gap is widened in order to obtain a thick foam,
The base resin is caused to foam internally in the extruder due to a decrease in the pressure of the base portion, or the corrugate is greatly exposed, so that it is difficult to obtain a good foam, and the thickness of the foam naturally obtained Could not be thickened.

Generally, when a thick polystyrene resin foam sheet is produced, the foam sheet is extruded into a tubular shape by a so-called extrusion foaming method, and air is supplied from the center of the die to form the foam sheet into a balloon shape. Then, while the inner surface of the balloon is not completely cooled and is in a bondable state, a means is employed in which a thick sheet is obtained by sandwiching the balloon with a pressing roll and bonding the inner surfaces together. This means utilizes the fact that the temperature on the inner surface side of the balloon immediately after extrusion is equal to or higher than the crystallization temperature of the resin to bond the inner surfaces of the balloon together to obtain a thick sheet. If such means were adopted as it was to obtain a thick-walled polypropylene-based resin foam in order to perform bonding while the temperature was high, the bubbles in the bonded portion would be crushed, and that part would be closed cells There is a problem that the rate becomes low, or a foaming agent gathers in that part, so-called void phenomenon appears, and in any case, the obtained foam has poor cushioning property. Was gone.

In view of these points, the applicant of the present application can increase the thickness of the foamed polypropylene resin sheet and improve the cushioning property of the foamed sheet if the foam shape is any. Intensive research was conducted from the viewpoint of the fact that the present invention was completed.

[0013]

That is, the polypropylene-based resin foam laminated sheet of the present invention has a drawdown property of 6%.
2. A thickness obtained by laminating a plurality of foam sheets each having a non-crosslinked propylene-based resin of 0 m / min or less as a base resin by melt-bonding the sheets in the width direction and the extrusion direction in the same direction. 0-20mm, density 0.02-0.3g / c
m ^{3 is} a foam laminated sheet, and in the cross section in the thickness direction of the laminated sheet, the shape of bubbles completely present in a portion exceeding the thickness of 0.8 mm from both surfaces of the sheet has the following conditional expressions (1) and (2). And the laminated sheet has a cell structure in which the closed cell rate of the laminated sheet is 80% or more (where a is a mean cell diameter in the thickness direction of the sheet, b is the average cell diameter in the sheet width direction, and c is the average cell diameter in the sheet extrusion direction). 0.4 ≦ a / b ≦ 1.4 (1) 0.4 ≦ a / c ≦ 1.4 (1) 2)

The foam laminated sheet of the present invention is a foam laminated sheet having a thickness of 3.0 to 10.0 mm and a density of 0.02 to 0.06 g / cm ³ within the range of the above constitutional requirements. In the cross section in the thickness direction of the laminated sheet, the number of air bubbles in the thickness direction is 5 to 20 and the shape of the air bubbles completely present in the surface layer having a thickness of less than 0.8 mm from both surfaces of the sheet is the following conditional expression (3). ) And (4) are preferably satisfied. 0.2 ≦ a / b ≦ 0.7 (3) 0.2 ≦ a / c ≦ 0.7 (() 4) On the other hand, when the density exceeds 0.06 g / cm ³ and 0.3 g / c
In the case of a foam laminate sheet of m ³ or less, the number of bubbles in the thickness direction is 5 to 25 in the cross section in the thickness direction of the laminate sheet, and is completely present in a surface layer portion having a thickness of less than 0.8 mm from both surfaces of the sheet. The shape of the bubble to be generated is represented by the following conditional expression (5),
(6) 0.3 <a / b ≦ 0.9 (5) 0.3 <a / c ≦ 0.9 (.) (6) is preferably satisfied, and this laminated sheet is suitable as a base material for molding automobile ceiling materials. The laminated sheet of the present invention may have a plate shape as well as a sheet shape that can be wound into a roll shape.

The non-crosslinked propylene resin used as the base resin of the foam sheet constituting the foam laminate sheet of the present invention may have a drawdown property of 60 m / min or less. The property is preferably 30 m / min or less, and more preferably 15 m / min or less. Further, a non-crosslinked propylene-based resin having a long-chain branch in the main chain is preferable because the drawdown property can be easily adjusted to the above range.

Incidentally, the draw-down property in the present invention means that a molten propylene resin heated to 230 ° C. is melted with a nozzle of a melt indexer (diameter 2.095 mm, length 8 m).
m), is extruded into a string at a constant speed of 10 mm / min. Then, the string is passed through a feed roll located above a tension detection pulley located below the nozzle, and then wound up by a take-up roll. On the other hand, the winding speed of the winding roll is gradually increased to cut the string, and the winding speed of the string at the time of cutting is referred to.

The non-crosslinked propylene resin may be any of a homopolymer, a block copolymer, and a random copolymer.
Olefins other than propylene are added in the copolymer in an amount of 0.5 to 30.
% By weight, particularly preferably 1 to 10% by weight. Examples of the olefin in this case include ethylene and α-olefins having 4 to 10 carbon atoms. Two or more can be used in combination.

Examples of the α-olefin having 4 to 10 carbon atoms include 1-butene, isobutylene, 1-pentene, 3-methyl-1-butene, 1-hexene, 3,4-dimethyl-1-butene, Examples thereof include 1-heptene, 4-methyl-1-pentene and 3-methyl-1-hexene.

The non-crosslinked propylene resin used as the base resin of the foam sheet is preferably a block copolymer from the viewpoint of the ease of forming the long chain branch in the main chain and the like. Particularly, a propylene-ethylene block copolymer is preferable.

The non-crosslinked propylene resin having a drawdown property of 60 m / min or less used in the present invention is a normal crystalline linear propylene resin (usually a weight average molecular weight of 100,000 or more). And a resin containing an atactic component or / and an isotactic but not crystallized component (hereinafter referred to as “normal propylene resin” in order to distinguish it from the propylene resin used in the present invention). Propylene-based resin), and when simply referred to as propylene-based resin, it means the resin used in the present invention), whereas the low-temperature decomposition type (decomposition temperature: room temperature to 12
(About 0 ° C.) and heated to 120 ° C. or lower to bind an atactic or / and non-crystallized isotactic component as a branched chain to the main chain of a normal propylene resin. It is thought to have a branched structure having long-chain branches mainly at the ends of the main chain.

The low-temperature decomposable peroxides include di (s-butyl) peroxydicarbonate and bis (2-
Ethoxy) peroxydicarbonate, dicyclohexylperoxydicarbonate, di-n-propylperoxydicarbonate, di-n-butylperoxydicarbonate, diisopropylperoxydicarbonate,
Examples thereof include t-butyl peroxy neodecanoate, t-amyl peroxy neodecanoate, t-butyl peroxy pivalate, and the like.

The propylene-based resin in the present invention is prepared by replacing the inside of the reaction vessel with an inert gas such as argon while stirring the ordinary propylene-based resin in a reactor equipped with a stirrer. Usually 5-5 per kg
It is obtained by adding 0 mmol and heating to about 120 ° C., preferably about 70 to 105 ° C. while continuing to stir and react (usually for 30 to 120 minutes), and then stopping the reaction. When terminating the reaction, a reaction terminator such as methyl mercaptan is introduced into the reaction vessel,
Alternatively, the reaction product is heated to about 130 to 150 ° C. for 20 to 4
A method of heating for 0 minutes is employed.

The drawdown property can be adjusted by the number and length of the long-chain branches. Generally, as the number of long-chain branches increases and the length of the branches increases, this value decreases. It tends to decrease. Therefore, in order to obtain a desired drawdown copolymer, it is necessary to set reaction conditions in consideration of these factors.

In general, if there is no long-chain branch, or if there is a branch, it is too short, the number of branches is small, or in the case of ordinary propylene-based resin, drawdown is used. The properties exceeded 60 m / min, and extrusion foaming was carried out using such a material to obtain a density of 0.02.
When obtaining a foamed sheet of about 0.3 g / cm ³ , the obtained foamed sheet has a large number of surface irregularities, so that the appearance as a product is poor, and the smoothness of the sheet is impaired. It becomes a cause of obstruction and has no commercial value. This is because, in the extrusion foaming method, immediately after the extrusion (that is, immediately after the resin is discharged from the die of the extruder), the bubbles instantaneously grow in the three-dimensional direction and are foamed. In ordinary propylene-based resins and the like, because the growth of bubbles is fast, foaming during sheet molding cannot be absorbed between the base and the mandrel,
This is because the portion becomes folds and remains on the sheet surface (generally, this is referred to as "corrugate").

Further, the crystallization time of the propylene resin used in the present invention at the crystallization temperature + 15 ° C. is preferably 800 seconds or more, more preferably 1000 seconds or more. For the measurement of the half-crystallization time, a crystallization rate measuring device can be used.

In order to measure the half-crystallization time, first, the support holding the film-like sample is put into an air bath of a crystallization rate measuring device to completely melt the sample, and then the molten sample is put together with the support. The sample is immersed in an oil bath maintained at the crystallization temperature of the sample + 15 ° C so as to block the optical path between the light source and the optical sensor, and is always kept at the optical sensor until the melted sample solidifies again. The voltage-time curve is obtained by adjusting the voltage of the light source so that the amount of light is detected. In this case the voltage at curve a voltage when a constant value was V _0, the voltage is a half-crystallization time of the time until the 1 / 2V _0.

In the present invention, not only the above-mentioned propylene-based resin can be used alone, but also if necessary, another resin can be mixed and used. Examples of the resin used as a mixture include propylene resins other than those described above, or high-density polyethylene, low-density polyethylene, linear low-density polyethylene, linear ultra-low-density polyethylene, ethylene-butene copolymer, and ethylene-anhydride. Examples include ethylene resins such as maleic acid copolymers, butene resins, vinyl chloride resins such as polyvinyl chloride and vinyl chloride-vinyl acetate copolymer, and styrene resins.

When the other resin is mixed in this way, the amount of the resin to be mixed is limited to 40% by weight of the total weight of the polymer after mixing. Needless to say, the drawdown property of the mixture is 60 m / min. It is necessary not to exceed.

As means for producing the foamed sheet constituting the foam laminated sheet of the present invention using the propylene-based resin as described above, usually, after melt-kneading the propylene-based resin and a foaming agent in an extruder, Using a circular die having an annular lip attached to the tip of the extruder, the melt-kneaded material is extruded and foamed from the lip of the die to obtain a tubular foam, and then the tube is cut open to form a sheet. Can be adopted.

In such a means, the width of the resin flow path near the opening of the circular die is narrowed (narrowed), or a mandrel for cooling the cylindrical foam extruded from the circular die is formed. A foam sheet having less unevenness in thickness is provided by adopting means such as blowing cooling air onto the outer surface of the tubular foam so as to cool from the inner surface side. Is preferable.

When a foamed sheet is obtained, an inorganic foaming agent, a volatile foaming agent, a decomposable foaming agent, or the like can be used as a foaming agent. Examples of the inorganic foaming agent include carbon dioxide, air, and nitrogen.

As the volatile foaming agent, propane, n
-Butane, i-butane, a mixture of n-butane and i-butane, pentane, an aliphatic hydrocarbon such as hexane, cyclobutane, a cycloaliphatic hydrocarbon such as cyclopentane, trichlorofluoromethane, dichlorodifluoromethane,
1,1-dichloro-1,1,1,2-tetrafluoroethane, 1,1-difluoro-1-chloroethane, 1,
Examples thereof include halogenated hydrocarbons such as 1,1,2-tetrafluoroethane, 1,1-difluoroethane, methyl chloride, ethyl chloride, and methylene chloride.

Further, examples of the decomposition type foaming agent include azodicarbonamide, dinitrosopentamethylenetetramine, azobisisobutyronitrile, sodium bicarbonate and the like. These foaming agents can be appropriately mixed and used.

The amount of the foaming agent varies depending on the type of the foaming agent, the desired expansion ratio, and the like.
The standard of the amount of the foaming agent used to obtain the foamed sheet of g / cm ³ is 0.5 volatile volatile agent per 100 parts by weight of the resin.
About 15 parts by weight (in terms of butane), 0.2 with inorganic foaming agent
About 8.0 parts by weight (in terms of carbon dioxide), and about 0.1 to 25 parts by weight of a decomposable foaming agent. In addition, density 0.02
The standard of the amount of the foaming agent used to obtain a foamed sheet of ^{3 to} 0.045 g / cm ³ is about 6 to 13 parts by weight (in terms of butane) of a volatile foaming agent per 100 parts by weight of the resin.

In order to obtain a foamed sheet, a foam regulator can be added to a melt-kneaded product of a resin and a foaming agent, if necessary. Examples of the cell regulator include inorganic powders such as talc and silica, acidic salts of polycarboxylic acids, and reaction mixtures of polycarboxylic acids with sodium carbonate or sodium bicarbonate. It is preferable to add the foam control agent in an amount of about 13 parts by weight or less per 100 parts by weight of the resin (except when a large amount of the inorganic filler is contained in the resin). Further, if necessary, additives such as a heat stabilizer, an ultraviolet absorber, an antioxidant, and a colorant can be added.

The resin may contain an inorganic filler up to 40% by weight of the total weight. Examples of the inorganic filler include talc, silica, calcium carbonate, clay, zeolite, alumina, barium sulfate, and magnesium hydroxide. Their average particle size is from 1 to 7
It is preferably 0 μm. When such an inorganic substance is contained in a large amount, the resulting foamed sheet has improved heat resistance and can reduce calorie burned during incineration.

[0037]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The polypropylene resin foam laminated sheet of the present invention will be described below in detail with reference to the drawings. FIG. 1 is an explanatory view showing an example of the production of the laminated sheet of the polypropylene resin foam of the present invention.

The foamed laminated sheet 1 of the present invention is used to push the foam sheets 2 and 3 prepared as described above separately in advance in the extrusion direction (hereinafter referred to as the “MD direction”) during their production.
) And the width direction (hereinafter, referred to as “TD direction”), and are laminated and integrated by melt-bonding to have a thickness of 3.0 to 20 mm and a density of 0.02 to 0.3 g / c.
m ^{3 is} a foam laminated sheet having an average cell diameter in the cross section in the thickness direction of the sheet 1 as a, an average cell diameter in the TD direction as b, and an average cell diameter in the MD direction as c. 1. In the thickness direction of the sheet, the shape of the bubble completely present in the inside exceeding 0.8 mm (hereinafter referred to as “central portion”) from both surfaces of the sheet is 0.4 ≦ a / b ≦ 1
4 and 0.4 ≦ a / c ≦ 1.4, and the laminated sheet has a cell structure with a closed cell ratio of 80% or more.

The foam structure of the foam laminated sheet 1 of the present invention has a three-layer structure which can be divided into two depending on the shape: air bubbles on the surface side (usually the uppermost side) and internal air bubbles. Since the air bubbles on the surface layer are not more than 0.8 mm in thickness from both surfaces of the sheet in the thickness direction of the sheet 1, the air bubbles completely present in the central portion in the present invention are the air bubbles located on the surface layer and the air bubbles located on the surface layer side. It can be considered to mean all other bubbles in the cross section of the sheet 1 except for the bubbles on the 0.8 mm line. However, the line with a thickness of 0.8 mm from both surfaces of the sheet in the thickness direction of the sheet does not always coincide with the line that bisects the bubble structure into the surface side and the internal bubbles depending on the shape, but at least a portion exceeding 0.8 mm. Is an internal bubble shape, and the object of the present invention is achieved by specifying the shape. Although the TD direction and the MD direction strictly define the sheet direction of the foam sheets 2 and 3, the foam laminated sheet 1 of the present invention divides the foam sheets 2 and 3 into their directional directions. Are made to coincide with each other so that the sheet direction of the foam laminated sheet 1 is adopted for convenience.

In order to obtain the foamed laminated sheet 1 of the present invention, the foamed sheets 2 and 3 are melt-bonded and integrated by lamination using a suitable means such as hot-air lamination using an apparatus as shown in FIG. For example, hot air is supplied from a dryer 6 (hot air generation source) to a layered surface of the foam sheet 2 sent from the feeding device 4 and another foam sheet 3 sent from another feeding device 5. The two sheets can be heated by being sprayed locally, laminated by pressing with a pressure roll 7 and then wound up by a winding device 8 to be continuously laminated and integrated. In addition, the foam sheet 2,
3 is not necessarily required to be the same as long as it is a non-crosslinked propylene-based resin foam, and the density, thickness and the like can be varied as needed.

The processing conditions such as the line speed, the gap between the pressure rolls, the distance from the hot air source to the pressure roll, the temperature of the hot air, the direction of the hot air spraying, and the like in the hot air laminating as an example of the above-mentioned two foam sheets to be laminated and integrated. 2,
3 is appropriately selected depending on the thickness, density, type of the base resin, and the like, but is usually 2 to 40 m / min. The foam sheets 2 and 3 are sent out at a line speed of
3, when the foam sheets 2 and 3 are simply overlapped,
Immediately before being sandwiched by pressure rolls set in a gap of 75 to 100% of the thickness, 0.02 to 0.2
This is performed by blowing hot air of 200 to 300 ° C. locally to the foam sheet laminated surface at a distance of 5 m. The foam laminate sheet 1 of the present invention is not limited to a laminate of two foam sheets, but may be a laminate of three or more foam sheets.

According to the present invention, not only the thickness of the foam sheet than the conventional foam sheet is made thicker, but also the shape of the bubbles formed in the center of the foam laminate sheet 1 is specified. Has a closed cell ratio of 80% or more to improve the buffering property. However, by laminating and integrating the foam sheets by a heating laminating means such as hot air laminating. , Foam laminated sheet 1 without lowering closed cell rate
The shape of the bubble formed at the center of the can satisfy the conditional expression as described above.

That is, before foam sheets 2 and 3 constituting foam laminate sheet 1 of the present invention are laminated, the shape of the bubbles present therein is in accordance with the conditions required in the present invention. The ratio of the average cell diameter b in the TD direction to the cell diameter a in the thickness direction and the average cell diameter c in the MD direction are not satisfied.
a / c = 0.32, and even if the bubble diameter a in the thickness direction of the sheet is shorter and flatter than the average bubble diameter b in the TD direction and the average bubble diameter c in the MD direction, It is considered that the air (or the residual foaming agent) existing in the bubbles expands during the lamination by the laminating means, whereby the bubbles extend in the thickness direction of the sheet, thereby satisfying the conditions required in the present invention.

Further, if the foam sheets 2 and 3 are laminated and integrated by using such a heating laminating means, the bubbles near the lamination surface are not crushed or communicated and the closed cell ratio is not reduced. The foamed sheet 1 exists in a shape substantially similar to that of the other air bubbles, and the so-called skin layer formed on the surface of the foamed sheets 2 and 3 during the production thereof has almost disappeared. There is no risk of affecting the buffering properties of In addition, even if corrugations exceeding the allowable range are generated on the surfaces of the foam sheets 2 and 3 before lamination, even after such lamination, such corrugations are alleviated to a level that does not cause a problem. Then, the inner surfaces of the foamed sheet extruded into a cylindrical shape by a so-called extrusion molding method are stuck together,
Since the thickness of the sheet is not increased and the air bubbles on the bonding surface are not crushed at the cost of halving the sheet width, the width of the obtained sheet 1 is not unnecessarily limited.

The foam-laminated sheet 1 of the present invention has a specific density and not only increases its thickness, but also has an air bubble existing at the center of the cross section in the thickness direction of the sheet 1 of 0.4 ≦
a / b ≦ 1.4 and 0.4 ≦ a / c ≦ 1.4 (a is the average cell diameter in the thickness direction of the sheet, b is the average cell diameter in the TD direction, and c is the average cell diameter in the MD direction. Diameter) that satisfies the relationship (diameter) and has a relatively long length in the thickness direction (hereinafter referred to as “vertical shape”), and is 80% or more without lowering the closed cell rate of the laminated sheet. It is particularly important to find that the foam laminated sheet is excellent in compressive strength, residual strain, flexural elasticity, maximum bending stress, etc. by keeping the foamed sheet in comparison with a conventional non-crosslinked propylene resin foam sheet. Also, it is possible to provide a sheet with excellent cushioning property and a firmness, and even if it is used by being formed into a packaging container or the like, it can be used to package even a relatively heavy one. Incidentally, the bubbles in the central portion are 0.5 ≦ a / b ≦ 1.1, 0.5 in terms of productivity.
It is preferable that ≦ a / c ≦ 1.1.

In the present invention, the bubble shape at the center is a /
When b <0.4 or a / c <0.4, the buffering property is insufficient, and when a / b> 1.4 or a / c>
In the case of 1.4, the sheet is poor in elongation and tends to tear. On the other hand, if the closed cell ratio is less than 80%, the compressive strength is insufficient and the residual strain increases, so that when used as a packaging sheet, packaging container, etc. For example, the cushioning property of a portion to which a load is applied becomes insufficient, and the elongation at the time of heat molding also deteriorates.

[0047] The present invention foamed laminate sheet is 25% compressive strength 0.35 kg / cm ² or more in the physical properties, in particular 2.0 kg / cm ² or more, the residual strain after 80% compression 4
0% or less, especially 25% or less, flexural modulus of 25 kg / c
m ² or more, particularly preferably 300 kg / cm ² or more. Incidentally, the compressive strength and the residual strain are necessary elements for maintaining the cushioning property of a portion to which a load is applied as a packaging material, and the flexural modulus is necessary for maintaining the stiffness of the sheet.

In the foam laminated sheet of the present invention,
When the thickness of the foamed sheet is less than 3.0 mm, it is inferior in deep drawing formability, cushioning property, mechanical strength, heat insulation, etc., and the thickness is 20%.
If it exceeds mm, it becomes inferior in the suitability of the packaging material other than the cushioning property, such as high bending strength and bulkiness. Further, when the density of the foamed sheet is less than 0.02 g / cm ^3, it is difficult to use as a fruit container or the like due to poor shape retention, and it is difficult to obtain a good appearance. 0.3g density
If it is more than / cm ³ , the stiffness is too strong, and it is not satisfactory in terms of cushioning. The density of the present invention the foam laminate sheet flexible ones 0.02~0.06g / cm ^3, further 0.023~0.045g / cm ^3, shape retention, preferably a good balanced buffering .

The thickness of the foam laminated sheet 1 of the present invention is 3.0 to 20 mm as described above, but the thickness is 3.0 in consideration of being subjected to heat molding, particularly deep drawing. １10.0mm, density is 0.02-0.06g
/ Cm ³ , and in the cross section in the thickness direction of the laminated sheet, there are 5 to 20 bubbles in the thickness direction, and the thickness is less than 0.8 mm in the thickness direction from both sheet surfaces (hereinafter, referred to as “surface layer portion”). ) Are 0.2 ≦ a / b ≦ 0.7 and 0.2 ≦ a / c
It is preferable that the shape satisfies the relationship of ≦ 0.7, that is, a bubble shape in which the bubble diameter in the MD and TD directions is longer than the bubble diameter in the thickness direction. In addition, the bubble completely present in the thickness direction less than 0.8 mm from both surfaces of the sheet is defined as all the bubbles in the cross section of the sheet 1 except for the bubble in the central portion and the bubble on the 0.8 mm line. means.

The sheet 1 has a thickness of 10 m.
m, it is difficult to uniformly heat the inside of the sheet at the time of thermoforming, and the air bubbles present in the central portion of the foam laminated sheet of the present invention may have a relatively vertical shape. If the number exceeds 20 and the density is 0.06
Even if it exceeds g / cm ³ , uniform heating becomes difficult, and the relationship between a / b and a / c representing the shape of bubbles located on the surface side existing in the surface layer portion is 0.2 or more and 0.7 or more. If it is below, the tensile strength of the sheet is sufficiently ensured, the elongation of the sheet at the time of heat forming is improved, and the deep drawing formability can be further improved along with the increase in the thickness of the sheet.
When a / b and a / c are less than 0.2, it is difficult to increase the thickness of the sheet. If it exceeds 0.7, the tensile strength will be insufficient.

The laminated foam sheet 1 of the present invention has the following features.
It is suitable for use as a container for fruits, a heat-resistant heat insulating material for construction, a sheet for packaging, and the like. In addition, when the laminated foamed sheet 1 of the present invention is molded and used, the molding method includes vacuum molding, air pressure molding, and application thereof such as free drawing molding, plug and ridge molding, ridge molding, and matched mold molding. , Straight forming, drape forming, reverse draw forming, air slip forming, plug assist forming, plug assist reverse draw forming, and a method combining these. Further, in consideration of sufficient compressive strength and flexural modulus, and further consideration of providing a shallow draw heat-forming material such as an automobile ceiling material, the thickness is 3.0 to 3.0.
Density exceeds 0.06 g / cm ³ at 20 mm, 0.3
g / cm ³ or less, and furthermore, 5 to 25 bubbles are present in the cross section in the thickness direction of the laminated sheet, and completely in the surface layer portion having a thickness of less than 0.8 mm from both sheet surfaces in the thickness direction. The shape of the existing bubbles is 0.3 <a / b
It is preferable that the shape has a shape that satisfies the relationship of ≦ 0.9 and 0.3 <a / c ≦ 0.9. When the thickness of the laminated sheet exceeds 20 mm or the number of bubbles exceeds 25, uniform heating during thermoforming becomes difficult, and a good product cannot be obtained even by shallow drawing. On the other hand, when the thickness of the laminated sheet is less than 3.0 mm or when the density is less than 0.3 mm.
If it is less than 06 g / cm ^3, it will be difficult to obtain strong compressive strength and bending elasticity. The same can be said for deep drawing, but when the number of bubbles is less than 5, it becomes difficult to secure a sufficient bending elastic modulus. Furthermore, when the relationship of a / b and a / c representing the bubble shape of the surface layer portion is 0.3 or less, it is difficult to obtain a strong compressive strength, and the a / b and a / c The relationship is 0.
If it exceeds 9, the density and the like are involved, and there is a possibility that unevenness in the thickness of the molded product may occur due to sagging of the sheet at the time of shallow drawing heating. Incidentally, in the above-mentioned shallow draw forming, as the forming method, the above-mentioned methods such as vacuum forming and pressure forming are mentioned. In addition, the adjustment of the bubble shape of the surface layer portion includes a method of adjusting the foam sheet before lamination, and a method of adjusting it at the time of lamination. For example, even if the base material is a propylene-based resin, the extrusion foaming temperature is adjusted to be low, and the extrusion foaming is performed by maintaining the pressure of the extruder die in a range of less than 80 kg / cm ² G, thereby performing extrusion foaming. It is possible to make the foam shape of the foam sheet from flat to nearly spherical. The foamed sheet of the present invention can be easily obtained by subjecting the product obtained by this method to lamination with hot air. As described above, a method of appropriately selecting the laminating conditions by hot air using a foam sheet having a flat cell shape in a cross section in the thickness direction can also be adopted.

Next, the present invention will be described in more detail with reference to specific examples (Examples 1 to 9) and comparative examples (Comparative Examples 1 to 4).

Examples 1 to 9 After melt-kneading a base resin and a foaming agent in an extruder, the melt-kneaded product was extruded and foamed from an annular lip of a circular die attached to the tip of the extruder to form a tubular foam. The tube was cut open to obtain a foamed sheet. Next, the obtained plurality of foam sheets were melt-bonded with each other by hot-air lamination to be laminated and integrated. The processing conditions at this time are as follows.

[Processing Conditions of Hot Air Laminate] Line speed 15 to 20 m / mi
n. -Crimping roll gap 80 to 98% of the total thickness of the foamed sheets to be laminated-Distance from hot air generation source 0.10 to 0.15
m ・ Hot air temperature 250 to 300 ° C. However, in Examples 2, 8 and 9, the line speed was 3 to 15 m / min. And

Comparative Examples 1 and 2 A tubular foam was obtained in the same manner as in the above example, and while the inner surface of the foam (balloon) was in a state where it could be bonded, the balloon was sandwiched by a pressing roll and the inner surface was bonded. A thick foam sheet was obtained.

Comparative Example 3 A laminated foam sheet was obtained in the same manner as in Example 3 except that the hot air temperature was changed to 400 ° C. among the processing conditions of the hot air laminate.

Comparative Example 4 A tubular foam was obtained in the same manner as in Example 4, and then the tube was cut open to form a sheet to obtain a conventional propylene-based resin foam sheet without hot-air lamination.

With respect to the obtained foam laminate sheet or foam sheet, the average cell diameter b in the TD direction and the average cell diameter c in the MD direction with respect to the average cell diameter a in the thickness direction in each of the surface layer portion and the central portion. Ratio (a / b, a /
c), number of bubbles in the thickness direction, sheet density, sheet thickness,
Table 1 shows the values obtained by measuring the closed cell ratio, and the results of measuring the compressive strength, residual strain, and flexural modulus of each of the foam laminated sheet and the foam sheet.

Further, using these foam laminated sheets or foam sheets, containers or automobile ceiling materials were molded, and the evaluation of the moldability is also shown in Table 1.

The resins used in Examples 1 to 9 and Comparative Examples 1 to 4 and the structure of the foam sheet are as follows.

[Substrate Resin of Foam Sheet, (Structure of Foam Laminated Sheet)] Example 1 Polypropylene "SD-632" manufactured by Highmont Corporation, USA
(Laminate product of two 2 × 30 mm foam sheets) Example 2 Polypropylene “SD-632” manufactured by Highmont USA,
(Laminated product of two 5 × 2 mm foam sheets) Example 3 Polypropylene “SD-632” manufactured by Highmont Corporation, USA
(Laminated product of two 20-fold 2 mm foam sheets) Example 4 Polypropylene "SD-632" manufactured by Highmont Corporation, USA
(Laminated product of two foam sheets of 20 times 3 mm) Example 5 Polypropylene "SD-632" manufactured by Highmont Corporation, USA
(Laminated product of four foam sheets of 20 × 3 mm) Example 6 Polypropylene “SD-632” manufactured by Highmont Corporation, USA
(Laminated product of two 20-fold 3 mm foam sheets and one 20-fold 2 mm foam sheet) Example 7 Polypropylene "SD-632" manufactured by Highmont Corporation, USA
(Laminated product of two 20-fold 2 mm foam sheets) Example 8 Polypropylene "SD-632" manufactured by Highmont Corporation, USA
(Laminated product of two foam sheets of 8 × 2 mm) Example 9 Polypropylene “SD-632” manufactured by Highmont Corporation, USA
(Laminated product of one foam sheet of 8 times 3 mm and one foam sheet of 8 times 4.5 mm)

The base resin of Comparative Examples 1 to 4 was made of polypropylene “SD-6” manufactured by Highmont Corporation in the same manner as in the above Examples.
32 "was used. Further, in Comparative Example 3, 20 times 2 m
m is a two-layered sheet of foam sheets.

[0063]

[Table 1]

* 1: The average cell diameter a in the thickness direction, the average cell diameter b in the width direction, and the average cell diameter c in the extrusion direction are the TD direction and MD direction of the foam laminate sheet or foam sheet, respectively. Obtain a microscopic enlarged photograph of a cross section in the thickness direction orthogonal to, and draw a line at a position corresponding to a position of 0.8 mm from the sheet surface based on the obtained photograph, divide the bubbles into a surface layer portion and a central portion, and About the bubble diameter of the part, the bubbles on the line drawn at the position corresponding to the position of 0.8 mm, and all the bubbles on the photograph except the bubbles at the center, and the bubble diameter at the center, on the line For all the bubbles on the photograph except for the bubbles in the surface layer portion, the bubble diameters in the thickness direction, the width direction, and the thickness direction and the extrusion direction were measured with calipers, and the average bubble diameters a and b were converted by the magnification of the photograph. , C was calculated.

* 2: Compressive strength was measured using a universal tester (Tensilon manufactured by Orientec Co., Ltd.) to measure a test piece 50 mm in length.
× Laminated so that the width is 50 mm and the thickness is about 25 mm,
10 mm / min. , And the load was measured.

* 3: The residual strain was measured using a universal testing machine (Tensilon, manufactured by Orientec Co., Ltd.) in the thickness direction at a rate of 10 mm / min. , And then depressurized at the same speed, and the residual strain at that time was measured.

* 4: The flexural modulus was measured using a universal testing machine (Co., Ltd.).
JIS-K-72 with Orientec Tensilon)
03, test specimen width 50mm, fulcrum distance 50mm
Was measured.

* 5: A foam laminated sheet or a foam sheet is heat-molded with a wooden mold and the opening diameter (outer diameter) is 13
5mm, bottom diameter (outer diameter) 105mm, depth (outer diameter) 8
A container with a 5 mm outer shape having a truncated cone shape was formed. The presence or absence of cracks and the uniformity of the thickness of the obtained container were observed, and the formability of the sheet was determined according to the following criteria.・ ・ ・: Good because there is no remarkably thin part in the thickness of the molded product. Δ: There is a part that is extremely thin in the molded product thickness. ×: Cracks and surface burns (a state where the surface is partially melted and the surface state is poor) are observed in the molded product. However, in Examples 2, 8, and 9, each sheet was vertically compressed using a head liner molding die to form a 180-degree sheet.
An automobile ceiling material having a size of 0 mm x 1400 mm in width and a concave curved shape having a depth of 80 mm was molded, and the moldability was determined based on the following criteria.・ ・ ・: The thickness of the ceiling material is uniform and good. Δ: There is uneven thickness in the ceiling material. ×: Cracks and surface burns are seen on the ceiling material.

* 6: The closed cell rate is a value obtained by the air pycnometer method (ASTM D 2856). However, since the volume of the sample becomes small due to the pressurization at the time of measuring the closed cell ratio of the polypropylene resin foam laminated sheet of the present invention and the measured value includes an error, the following correction is performed.

Calculation of Correction Coefficient A square sample of 25 mm in length and 25 mm in width is stacked from the laminated sheet to obtain a number of measurement samples having a thickness of about 3.5 cm. The obtained measurement sample was placed in water 1a.
The sample is immersed in a pressure-resistant container of tm for 30 minutes, and the volume of the sample: Vw (cm ³ ) is determined from the difference between the water level before the sample is immersed and the water level after lapse of 30 minutes. Next, the pressure in the pressure vessel is left at 1 atm to 2 atm for 5 minutes, and the difference between the water level at a pressure of 1 atm and the water level after standing at 2 atm for 5 minutes: ΔV (cm ³ ) is determined. V above
From w and ΔV, the correction coefficient α is obtained by the following equation. Correction coefficient: α = Vw / (Vw−ΔV)

Correction of Sample Volume In the same manner as the calculation of the correction coefficient, a square sample having a side of 25 mm is stacked and the number of measurement samples is about 3.5 cm, and the air pycnometer method is used in accordance with ASTM D2856. Actual volume of sample: Vx (cm ³ )
Ask for. The obtained Vx is multiplied by the correction coefficient α to obtain Vx
Is corrected, and the actual volume after the correction is: V'x (cm ³ ) = Vx (cm ³ ) ×
V′x is obtained as α.

Calculation of closed cell ratio V'x (cm ³ ) obtained as described above and apparent volume Va (cm ³ ) obtained from the outer dimensions of the measurement sample, and the open cell ratio: Fo ( %), And the closed cell ratio: Fc (%) is calculated by the following equation from the value of the open cell ratio, the foam density: ρf (g / cm ³ ), and the resin density: ρs (g / cm ³ ). Was. Open cell ratio: Fo (%) = [(Va−V′x) / Va]
× 100 Closed cell rate: Fc (%) = 100−Fo−ρf / ρs

FIG. 2 is a view schematically showing an air pycnometer, in which 10 is a reference cylinder, 11 is a piston of a reference cylinder 10, 12 is a sample cylinder, 13 is a piston of a sample cylinder,
14 is a pressure display device. The sample 15 is placed in the sample cylinder 12, and the piston 11 of the reference cylinder 10 is placed in the Positio shown by ASTM D2856.
In the state of n 1 (when the piston 11 is at the position A in the figure), the pressure in the reference cylinder 10 is 1
atm, and when in the position 2 (when the piston 11 is at the position B in the figure), the pressure in the reference cylinder 10 becomes 2 atm.
Is adjusted to obtain the actual volume Vx (cm ³ ) of the measurement sample. Piston 1 of reference cylinder 10
Difference between the internal volume of the reference cylinder 10 when 1 is in the position 2 and the internal volume of the sample cylinder 12 when the pressure is 2 atm (hatched portion in the figure)
Is determined as the actual volume Vx of the sample.

* 7: The number of cells in the thickness direction was obtained by obtaining an enlarged microscopic photograph of the foam laminate sheet or a cross section in the thickness direction of the foam sheet, and drawing a straight line in the thickness direction based on the obtained photograph.
This is a value obtained by counting the number of bubbles crossed by the straight line.

As shown in Table 1, the propylene-based resin foam laminated sheet of the present invention has a compression strength of 0.35 kg / cm ³ or more and a residual strain of 40% in Examples 1 to 9.
Hereinafter, the flexural modulus shows a value of 25 kg / cm ² or more, and the sheets of Examples 2, 8 and 9 have a compressive strength of 2 k.
g / cm ² or more, residual strain of 25% or less, flexural modulus of 300 kg / cm ² or more, excellent in various physical properties, cushioning property as compared with the conventional propylene resin foam sheet shown in Comparative Example 4, It is also excellent in the strength of stiffness.

[0076]

As described above, the polypropylene-based resin foam laminated sheet of the present invention has a drawdown property of 60.
The thickness obtained by laminating a plurality of foam sheets using a non-crosslinked propylene-based resin having a m / min or less as a base resin by melt-bonding them in such a manner that their width directions and extrusion directions match. 3.0-20mm, density 0.02-0.3
g / cm ^{3 in} the foam laminated sheet, and in the cross section in the sheet thickness direction, air bubbles completely present in a portion exceeding the thickness of 0.8 mm from both surfaces of the sheet have an average cell diameter a in the sheet thickness direction, The average cell diameter b in the width direction and the average cell diameter c in the sheet extrusion direction are 0.4 ≦ a.
/B≦1.4 and 0.4 ≦ a / c ≦ 1.4, and the laminated sheet has a closed cell ratio of 80.
% Or more, it has excellent physical properties such as compressive strength, residual strain, bending elasticity, and maximum bending stress. It has a sufficient thickness compared to conventional propylene-based resin foam sheets, and has cushioning and stiffness. Are improved, and the above-mentioned physical properties are also satisfactory.

Further, the thickness of the laminated sheet of the present invention is 3.0 to 10.0 mm and the density is 0.0
2 to 0.06 g / cm ³ , the number of air bubbles in the thickness direction in the cross section of the laminated sheet in the thickness direction is 5 to 20, and air bubbles completely present in a surface layer portion having a thickness of less than 0.8 mm from both surfaces of the sheet. Is 0.2 ≦ a / b ≦ 0.7, 0.
Assuming that the relationship of 2 ≦ a / c ≦ 0.7 is satisfied,
The sheet can be heated uniformly even to the inside of the sheet at the time of thermoforming, and the tensile strength of the sheet is sufficiently ensured, the elongation of the sheet at the time of thermoforming is improved, and the sheet thickness is increased. Since the drawability can be further improved, it becomes suitable for being subjected to heat molding. Further, the thickness of the polypropylene-based resin foam laminated sheet of the present invention is ³ to 20 mm, the density is more than 0.06 g / cm ³ ,
g / cm ³ or less, the number of bubbles in the thickness direction of the laminated sheet is 5 to 25, and 0.8 m from both surfaces of the sheet.
bubble shape completely present in the surface layer of less than 0.3 m
/B≦0.9 and 0.3 <a / c ≦ 0.9, the compression strength is high, and the tensile strength of the sheet is adjusted to the extent that the sheet is prevented from being deformed during heat molding. Thus, shallow drawing can be performed, and in addition to the above-described sufficient compressive strength, a sufficient bending elastic modulus is also realized, so that the base material for forming an automobile ceiling material is excellent.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing one production example of a polypropylene resin foam laminated sheet of the present invention.

FIG. 2 is a schematic diagram of an air pycnometer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Foam laminated sheet 2 Foam sheet 3 Foam sheet

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Akinori Taira 1078-4 Komaocho, Utsunomiya-city, Tochigi Pref. Casa Eye 202 (58) Field surveyed (Int. Cl. ⁶ , DB name) B32B 1/00- 35/00 B60R 13/02-13/08

Claims (4)

(57) [Claims] 1. A method of melt-bonding a plurality of foam sheets each having a drawdown property of 60 m / min or less and a non-crosslinked propylene-based resin as a base resin so that the width direction and the extrusion direction match. Thickness of 3.0 to 2
A foam laminate sheet having a thickness of 0 mm and a density of 0.02 to 0.3 g / cm ³ , wherein the shape of bubbles completely present at a portion exceeding 0.8 mm in thickness from both surfaces of the sheet in the cross section in the thickness direction of the laminate sheet is as follows: Characterized by satisfying conditional expressions (1) and (2), and having a cell structure in which the closed cell ratio of the laminated sheet is 80% or more (wherein the conditional expression a is the average cell diameter in the sheet thickness direction, b is the average cell diameter in the sheet width direction, c
Is the average cell diameter in the sheet extrusion direction). 0.4 ≦ a / b ≦ 1.4 (1) 0.4 ≦ a / c ≦ 1.4 (1) 2) 2. The thickness is 3.0 to 10.0 mm and the density is 0.
A foam laminated sheet of 02 to 0.06 g / cm ³ ,
In the cross section in the thickness direction of the laminated sheet, the number of bubbles in the thickness direction is 5 to 20 and the shape of the bubbles completely present in the surface layer portion having a thickness of less than 0.8 mm from both surfaces of the sheet is the following conditional expression ( The polypropylene resin foam laminated sheet according to claim 1, which satisfies 3) and (4), wherein a is an average cell diameter in the thickness direction of the sheet, b is an average cell diameter in the width direction of the sheet, c is the average cell diameter in the sheet extrusion direction). 0.2 ≦ a / b ≦ 0.7 (3) 0.2 ≦ a / c ≦ 0.7 (() 4) 3. The method according to claim 1, wherein the density exceeds 0.06 g / cm ³ ,
3 g / cm ³ or less of a foam laminated sheet, wherein the number of cells in the thickness direction is 5 to 5 in the cross section in the thickness direction of the laminated sheet.
25 pieces and 0.8 mm thick from both sides of the sheet
2. The polypropylene resin foam laminate sheet according to claim 1, wherein the shape of the air bubbles completely present in the surface layer portion satisfying the following conditional expressions (5) and (6): (where a is the thickness direction of the sheet) , B is the average cell diameter in the sheet width direction, and c is the average cell diameter in the sheet extrusion direction). 0.3 <a / b ≦ 0.9 (5) 0.3 <a / c ≦ 0.9 (5) 6) 4. A base material for molding an automobile ceiling material, comprising the polypropylene resin foam laminate sheet according to claim 3.