JPH08231745A - Polypropylene-based resin laminar foam and middle partition material comprising the same - Google Patents

Abstract

PURPOSE: To provide a foam having more excellent punchability than that of a conventional foam, improved cushioning properties, being relatively thick, having excellent compression strength and flexural strength. CONSTITUTION: This polypropylene-based resin laminar foam 1 is a single layer laminar foam and has 0.3-0.06g/cm<3> density. The shape of cells 2 existing in the interior exceeding 25% the whole thickness from both the surfaces of the foam, respectively, in the section in the thickness direction of the foam satisfies the formula (1), 0.45<=A/B<=1.0 and the formula (2), 0.45<=A/C<=1.0 (A is the average value of the diameter (a) of each cell 2 in the thickness direction; B is an average value of the diameter (b) of each cell 2 in the MD direction of the foam; C is the average value of a diameter (c) of each cell 2 in the TD direction of the foam. Consequently, since the foam has excellent processability, it can be processed into a desired size and a shape at a low cost, and an inexpensive curing sheet and a middle partition material of a desired size and shape having excellent cushioning properties and durability can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polypropylene-based resin plate-like foam and a partitioning member made of the plate-like foam.

[0002]

2. Description of the Related Art As a single-layer polypropylene resin plate-like foam, a conventionally known one is a product obtained by extrusion foam molding by a T-die method. Low magnification (density 0.3 g/
cm ³ ), and the plate-like foam surface has a solid layer formed on it, and the rigidity is too high.
It was difficult to process. That is, since the punching blade bends to the outside immediately, there is a possibility that an error occurs in the processing dimension, and in order to prevent this, the maintenance of the punching blade must be strictly performed. Furthermore, even if maintenance is performed, since the object to be machined is hard in the first place, the cutting edge of the cutting blade itself is likely to be damaged, and the life of the cutting blade is short. If the life of the punching blade is short, not only the machining cost will be high by simply using a large number of punching blades, but also the replacement of the punching blades and the positioning to enable accurate machining without dimensional error. There is also a problem that an increase in processing cost due to an increase in various operations is unavoidable.

Further, when it is attempted to obtain a (middle) partitioning material or the like which is used by combining the plate-like foam with a fitting groove, etc., the plate-like foam is hard. However, it is difficult to correct the dimensional error by crushing, distorting or misaligning a little.Therefore, if the dimensions such as the position and width of the mating groove are not accurately machined, the grooves will be appropriate. It becomes impossible to incorporate into. In particular, since the conventional plate-like foam is liable to have a dimensional error during the punching process as described above, it is difficult to obtain a partitioning material in which the grooves can be properly incorporated.

Further, since the above-mentioned conventional plate-like foam has a high density and its surface is solid, that is, hard and smooth,
It had poor cushioning properties and was slippery, and was unsuitable for applications such as a curing sheet, and also unsuitable as a partitioning material.

In addition, in the slit-opening method in which a foamed sheet extruded in a tubular shape by extrusion foaming with an annular die is cut open into a plate shape, the thickness and bending strength of the foamed body and the smoothness due to the bending of the sheet, etc. However, none of them were sufficiently obtained.

On the other hand, a tubular foam sheet extruded into a tubular shape by extrusion foam molding with an annular die is pressed by a roll while the inner surface is not completely cooled and is in a bondable state. In the laminating method in which the inner surface is laminated to form a plate, the process of crushing the cylinder is used, so the thickness is about twice as large as that of the slit-opening method, but the width is about a half. However, there is a big drawback that a wide one cannot be obtained.

Further, in order to obtain a wide one in the above-mentioned laminating system, the entire apparatus including the extruder has to be upsized. However, if the apparatus is upsized, the molding conditions are changed accordingly. There is a problem in that the equipment cost must be increased, which leads to an increase in manufacturing cost, and it also takes a great deal of time to find an appropriate molding condition. When the molding conditions are changed in accordance with the increase in size of the apparatus, it is not necessary to change them proportionally according to the enlargement ratio, but they must be changed fundamentally, so the above disadvantages occur.

The present invention has been made in view of the above points, and solves the above-mentioned drawbacks of the prior art, has a large thickness, a high expansion ratio, is excellent in punching workability, and is excellent in cushioning property. It is an object of the present invention to provide a single-layer polypropylene-based resin plate-like foam that can be manufactured at a relatively low cost.

[0009]

DISCLOSURE OF THE INVENTION The present invention is a single-layered plate-like foam having a density of 0.3 to 0.06 g/cm ³ and a total thickness from both surfaces of the foam in a cross section in the thickness direction of the foam. Polypropylene-based resin plate-shaped foam, characterized in that the shape of bubbles present in the interior exceeding 25% of each thickness satisfies the following conditional expressions (1) and (2): 0.45≦A/B≦1. 0・・・・・・(1) 0.45≦A/C≦1.0・・・・・・(2) [where A is the average in the thickness direction of the foamed body] Bubble diameter, B
Is the average cell diameter in the foam extrusion direction (MD direction), C is the average cell diameter in the direction (TD direction) perpendicular to both the foam extrusion direction and the thickness direction] Thickness 2 to 7 mm, density 0.18 to 0 0.09 g/c
m ^3, compression strength 1~7kg / cm ^2, MD direction polypropylene resin shaped foam having an average flexural strength described above is 10 to 70 kg / cm ² and TD direction, a center line average roughness (Ra The surface roughness shown by 5) is 5 to 50 μm.
The gist is the above-mentioned or the above-mentioned polypropylene-based resin plate-shaped foam, and the partitioning member comprising the polypropylene-based resin plate-shaped foam according to any one of the above items.

The present invention will be described in detail below with reference to the drawings. FIG. 1(a) is a cross section in the thickness direction along the extrusion direction (hereinafter referred to as MD direction) of the polypropylene-based resin plate-shaped foam of the present invention, and FIG. 1(b) is the extrusion of the polypropylene-based resin plate-shaped foam of the present invention. It is a schematic diagram based on a microscope enlarged photograph showing each cross section in the thickness direction along a direction perpendicular to the direction (hereinafter, referred to as TD direction), and is a diagram for explaining a cell shape of the plate-shaped foam of the present invention. Bubbles in the surface layer are omitted in the figure. In the figure, 1 represents a polypropylene-based resin plate-like foam of the present invention, and 2 represents bubbles. Also, a
(A ₁ , a ₂ , a ₃ ... _An ) are the diameters of the cells 2 in the thickness direction of the plate-like foam 1, b(b ₁ , b ₂ , b ₃ ... b)
_n ) is the diameter in the MD direction of the plate-like foam 1 of cells 2, c
(C ₁ , c ₂ , c ₃ ... C _n ) respectively represent the diameter of the plate-like foam 1 of the cells 2 in the TD direction. The extrusion direction (MD direction) in the plate-shaped foam 1 refers to the direction in which the resin is extruded when the plate-shaped foam 1 is obtained using an extruder. The TD direction is a width direction with respect to the extrusion direction.

The polypropylene resin plate-like foam 1 of the present invention is a single-layer plate-like foam and has a density of 0.3 to 0.
It is 06 g/cm ³ . Then, it is the average of a [(a
₁ +a ₂ +a ₃ +...+a _n )/n] is replaced with A, and the average of b is [(b ₁ +b ₂ +b ₃ +...+b
_n )/n] is replaced with B, and is the average of c [(c ₁ +
c ₂ +c ₃ +... +c _n )/n] is replaced by C (where n is 20 or more), and the thickness direction sectional view of the foam 1 is shown in FIGS. 1(a) and 1(b). In each of the two surfaces S, S of the foam 1 at a position of 25% of the total thickness T of the foam 1 (ie, 0.25 each from both surfaces S, S).
The shape of bubbles existing within the range of thickness T of 0.5 T at the center portion in the thickness direction, which exceeds T, satisfies both the following conditions (1) and (2). 0.45≦A/B≦1.0 (1) 0.45≦A/C≦1.0 (2)

Therefore, in the present invention, 0.45≦[(diameter in the thickness direction of the plate-shaped foam 1)/(diameter in the MD direction of the plate-shaped foam 1)]≦ in each of the bubbles 2.
It is not necessary to be 1.0, and it is not necessary that 0.45≦[(diameter in the thickness direction of the plate-shaped foam 1)/(diameter in the TD direction of the plate-shaped foam 1)]≦1.0. .. That is, for example, 0.45≦a ₁ /b ₁ ≦1.0 does not necessarily have to be satisfied, and 0.45≦a ₁ /c ₁ ≦1.0 does not necessarily have to be satisfied.

Further, in the present invention, for each bubble 2,
The average value of all cells in the value of [(diameter in the thickness direction of the plate-shaped foam 1)/(diameter in the MD direction of the plate-shaped foam 1)] is 0.45.
It is not more than 1.0 and not less than 1.0, and for each bubble 2, [(diameter in the thickness direction of the plate-shaped foam 1)
The average value of all cells in the value of /(diameter of the plate-shaped foam 1 in the TD direction)] is not 0.45 or more and 1.0 or less. That is, 0.45≦[(a ₁ /b ₁ )+
(A ₂ /b ₂ )+(a ₃ /b ₃ )+...+(a _n /b
_n )]/n≦1.0, and 0.45≦[(a
₁ /c ₁ )+(a ₂ /c ₂ )+(a ₃ /c ₃ )+...
+(a _n /c _n )]/n≦1.0 is not satisfied.

In the present invention, the bubble 2 in FIG.
_{As shown in 0} , each of the two surfaces S and S of the plate-shaped foam 1 is located at a position of 25% of the total thickness T of the plate-shaped foam 1, that is, on each line of 0.25T from both surfaces S and S. If it takes to have (contact including the case in which) bubbles present, the above condition (1) for the bubble 2 ₀ and (2) and will not be applied. Thus whether the bubbles 2 ₀ satisfies the conditions (1) and (2) are not a problem.

Note that a ₁ , a ₂ , a ₃ ...
a _n , b ₁ , b ₂ , b ₃ ... b _n , c ₁ , c ₂ ,
The value of c ₃ ····· c _n (n is 20 or more), as shown in FIG. 7, the thickness direction, MD direction or TD direction, and should be adopted maximum tangent line spacing tangent to each bubble To do.

In the present invention, by satisfying the above conditions (1) and (2), it is possible to obtain a sufficient compressive strength which could not be realized by a sheet as a plate material, and further, a plate-like foam having a large thickness. Becomes Among the ranges of the above conditions (1) and (2), those satisfying 0.6≦A/B≦1.0 and 0.6≦A/C≦1.0 are particularly preferable.

Further, in the present invention, the shape of cells existing in the inside of more than 25% of the total thickness from both surfaces of the foam is specified.
By satisfying the above conditions (1) and (2) also in the shape of bubbles existing in the surface layer portion within the range of %, the compressive strength and the thickness tend to be further increased, which is preferable.

The propylene resin used as the base resin in the present invention has a drawdown property of 60 m/min or less, preferably 30 m/min or less, more preferably 15 m/min.
/Min or less of non-crosslinked propylene resin. A non-crosslinked propylene-based resin having a long chain branch in the main chain can be easily used in the present invention because its drawdown property can be easily adjusted within the above range.

The term "drawdown property" as used in the present invention means that the molten propylene resin heated to 230° C. by using the apparatus shown in FIG. 6 is the nozzle 61 of the melt indexer.
(Diameter 2.095 mm, length 8 mm), at a piston pressing speed of 10 mm/min, extruded in the form of a string in the direction of the arrow in the figure, and then the string-shaped object was positioned above the tension detecting pulley 62 located below the nozzle. Feed rolls 63, 64, 6
After passing 4, the winding speed of the winding roll is gradually increased while being wound by the winding roll 65 to cut the string-like object, and the winding speed of the string-like object at the time of this cutting is changed. I will say. The distance L ₁ between the nozzle 61 and the pulley 62 is 250 mm, the diameter R of the pulley 62 is 45 mm,
The distance L ₂ between the pulley 62 and the feed roll 63 is 90 m
m, the distance L ₃ between the feed rolls 63 and 64 is 45 mm,
The angle θ of the tangent line extending from the contact surface of the feed rolls 64, 64 to the upper surface of the feed roll 63 with respect to the horizontal plane is 40°.

Further, as the base resin in the present invention, in addition to the above drawdown property, it is preferable that the melt tension is 10 g or more because the surface condition of the plate-like foam can be improved. The melt tension is determined by the melt indexer nozzle 6
1 is the value (g) detected by the load cell 66 connected to the movable pulley 62 below the nozzle 61 to which the resin extruded in a string shape from the first is applied, and is the same as the above-described drawdown property measurement. It is measured by the equipment and conditions. More specifically, the melt tension increases as the winding speed of the winding roll increases, and then reaches a steady state.
The steady state here is a state in which the melt tension is stable with a width between the maximum value and the minimum value. Therefore, the winding speed indicating the above state is used as the winding speed for obtaining the melt tension, and the average value of the melt tension in the steady state detected by the load cell at that time is adopted as the melt tension. It should be noted that if the winding speed is too fast, the string-shaped resin will be cut off, or the string-shaped resin will become thinner and thinner and the melt tension will decrease.

The non-crosslinked propylene resin may be a homopolymer, a block copolymer or a random copolymer. In the case of a copolymer, propylene and an olefin other than propylene are copolymerized. 0.5 in polymer
What is contained at a rate of up to 30% by weight, particularly 1 to 10% by weight is preferable, and in this case, the olefin may be ethylene or an α-olefin having 4 to 10 carbon atoms. Alternatively, two or more kinds 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 and 3,4-.
Dimethyl-1-butene, 1-heptene, 4-methyl-1
-Pentene, 3-methyl-1-hexene and the like can be mentioned.

From the standpoint of ease of forming long-chain branches in the main chain, the non-crosslinked propylene-based resin used as the base resin for the plate-like foam is preferably a block copolymer. Particularly preferred is a propylene-ethylene block copolymer.

The non-crosslinked propylene-based resin having a drawdown property of 60 m/min or less used in the present invention is an ordinary crystalline linear propylene-based resin (usually a weight average molecular weight of 100,000 or more). And a resin containing an atactic component and/or a component that is isotactic but is not crystalline therein (hereinafter, this resin is referred to as "normal propylene" in order to distinguish it from the propylene resin used in the present invention. When referred to as "resin-based resin" and simply referred to as propylene-based resin, it means a resin used in the present invention. In contrast to low temperature decomposition type (decomposition temperature: room temperature to 12
(0° C.) and mixed with a peroxide and heated to 120° C. or lower to bond an atactic or/and non-crystallized isotactic component as a branched chain to the main chain of a normal propylene resin. Obtainable. The non-crosslinked propylene-based resin thus obtained is considered to have a branched structure having long-chain branches mainly at the ends of the main chain.

Examples of the low temperature decomposition type peroxide include di(s-butyl)peroxydicarbonate and bis(2-
(Ethoxy) peroxydicarbonate, dicyclohexyl peroxydicarbonate, di-n-propylperoxydicarbonate, di-n-butylperoxydicarbonate, diisopropylperoxydicarbonate,
Examples thereof include t-butyl peroxy neodecanoate, t-amyl peroxy neodecanoate, t-butyl peroxypivalate and the like.

The propylene-based resin in the present invention is a conventional propylene-based resin, in which the inside of the reaction vessel is replaced with an inert gas such as argon while stirring in a reaction group equipped with a stirrer, and then the above-mentioned peroxide is used as a resin. Usually 5 to 5 per kg
0 mmol is added, and the mixture is heated to about 120° C., preferably about 70 to 105° C. while continuing stirring to react (usually for 30 to 120 minutes), and then the reaction is stopped to obtain. Incidentally, in stopping 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 40° C.
A method of heating for a minute or the like is adopted.

The drawdown property can be adjusted by the number and length of the above long chain branches. Generally speaking, the larger the number of long chain branches and the longer the branch length, this value is It tends to decrease. Therefore, in order to obtain a copolymer having a desired drawdown property, it is necessary to set the reaction conditions in consideration of these things.

In general, if there is no long-chain branch, or if there is branch, it is too short, the number of branches is small, or in the case of a normal propylene resin, drawdown. The sex exceeds 60 m/min. In the present invention, as will be described later, a sheet-like foam foam is first obtained by extrusion foaming, and then the sheet-like foam is formed into a plate shape.
When extrusion foaming is performed using a resin exceeding 0 m/min to obtain a sheet-like foam having a density of 0.3 to 0.06 g/cm ³ , the resulting sheet-like foam has many surface irregularities. The appearance of the product is not good, and the smoothness of the foam is impaired, which causes a hindrance to secondary processability and moldability, resulting in no commercial value. this is,
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 are instantly grown in the three-dimensional direction to form the foam. In the case of propylene resin, etc., the growth of bubbles is so fast that the foam cannot be absorbed between the die and the mandrel when the sheet-shaped foam is molded, and that part becomes pleated and becomes a foam surface. This is because it remains (generally referred to as a "corrugate").

Further, the propylene-based resin used in the present invention preferably has a half-crystallization time at the crystallization temperature +15° C. of 800 seconds or longer, and particularly preferably 1000 seconds or longer. A crystallization rate measuring device can be used for the measurement of the semi-crystallization time.

In order to measure the semi-crystallization time, first, the support holding the film-like sample is placed in the air bath of the crystallization rate measuring instrument to completely melt the sample, and then the melted sample is put together with the support. Immersion 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, the optical sensor, and a fixed amount of light is detected by the optical sensor until the molten sample solidifies again. The voltage of the light source is adjusted to obtain the voltage-time curve. When the voltage when the voltage on this curve becomes a constant value is V ₀ , the time until the voltage becomes 1/2 V ₀ is the half-crystallization time.

In the present invention, not only the above propylene-based resin may be used alone, but other resins may be mixed and used as required. Examples of the resin to be mixed and used are propylene-based resins other than the above, or high-density polyethylene, low-density polyethylene, linear low-density polyethylene, linear ultra-low-density polyethylene, ethylene-butene copolymer, ethylene-anhydrous. Examples thereof include ethylene-based resins such as maleic acid copolymers, butene-based resins, polyvinyl chloride, vinyl chloride-based resins such as vinyl chloride-vinyl acetate copolymers, and styrene-based resins.

When other resins are 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, and needless to say, the drawdown property of the mixture is 60 m/min. Must not exceed.

As the foaming agent used in the present invention, an inorganic foaming agent, a volatile foaming agent, a decomposable foaming agent or the like can be used. 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, linear aliphatic hydrocarbons such as pentane and hexane,
Cycloaliphatic hydrocarbons such as cyclobutane and cyclopentane, trichlorofluoromethane, dichlorofluoromethane, 1,1-dichloro-1,1,1,2-tetrafluoroethane, 1,1-difluoro-1-chloroethane,
1,1,1,2-tetrafluoroethane, 1,1-difluoroethane, methyl chloride, ethyl chloride,
Examples thereof include halogenated hydrocarbons such as 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.

Although the amount of the foaming agent used varies depending on the kind of the foaming agent, the desired expansion ratio, etc., the final density is 0.3.
The amount of the foaming agent used to obtain a plate-like foam of 0.06 g/cm ³ is about 0.8 to 6.0 parts by weight of volatile foaming agent per 100 parts by weight of resin (butane conversion), About 0.6 to 4.5 parts by weight of inorganic foaming agent (converted to carbon dioxide),
Decomposition type foaming agent is about 2 to 11 parts by weight (sodium bicarbonate equivalent). Finally, the density is 0.18 to 0.09.
The standard of the amount of the foaming agent used to obtain a plate-like foam of g/cm ³ is 1.6 volatile foaming agent per 100 parts by weight of the resin.
About 3.3 parts by weight (butane conversion), 1.
It is about 2 to 2.5 parts by weight (converted to carbon dioxide) and about 3.3 to 7 parts by weight of the decomposition type foaming agent (converted to sodium bicarbonate).

In obtaining the sheet-shaped foamed product, if necessary, a foam control agent can be added to the melt-kneaded product of the resin and the foaming agent. Examples of the bubble control agent include inorganic powders such as talc and silica, acidic salts of polyvalent carboxylic acids, and reaction mixtures of polyvalent carboxylic acids with sodium carbonate or sodium bicarbonate. It is preferable to add about 5 parts by weight or less of the cell regulator per 100 parts by weight of the resin (however,
Except when a large amount of inorganic filler is contained in the resin, which will be described later). Further, if necessary, additives such as a heat stabilizer, an ultraviolet absorber, an antioxidant and a colorant may be added.

In addition, 50% by weight of the total weight is previously contained in the resin.
Inorganic additives may be contained up to the limit. Examples of the inorganic filler include talc, silica, calcium carbonate,
Examples include clay, zeolite, alumina, barium sulfate, magnesium hydroxide and the like. The average particle size of these is 1 to
It is preferably 70 μm. When a large amount of such an inorganic filler is contained, the obtained sheet-like foam has improved heat resistance and can reduce the calories burned during incineration.

The plate-like foam 1 of the present invention has a specific density and a high expansion ratio, and the bubbles existing in the central portion of the cross section in the thickness direction of the foam 1 satisfy the above-mentioned conditions. Since it has a bubble shape that is long in the thickness direction (hereinafter referred to as a vertical shape), it has excellent workability as well as excellent cushioning properties, and it is relatively thick and also compressed. It has excellent strength and bending strength.

In the present invention, when the density of the plate-shaped foam 1 is less than 0.06 g/cm ^3, it cannot be used as a plate because it is poor in shape retention and easily bends and is difficult to form a plate. On the other hand, if the density exceeds 0.3 g/cm ³ , the rigidity becomes too strong, resulting in poor buffering properties and poor punching workability.

Further, the total thickness of the foam is 25 from each surface.
If the shape of the bubbles present in the interior exceeding 100% is less than the above condition range, the rigidity as a plate material such as compressive strength and bending strength becomes insufficient, and if it exceeds the above condition range, the rigidity is excessive, and It is difficult to manufacture while maintaining closed cells to some extent.

Particularly in the present invention, the density of the plate-like foam 1 is preferably 0.18 to 0.09 g/cm ³ . Within this range, the rigidity and the cushioning property are well balanced, and the sufficient rigidity suitable for use as a plate-like body and the appropriate secondary cushioning property such as the punching process and the cutting process are provided. It can be a plate-shaped foam.

In the present invention, the compressive strength of the plate-like foam 1 is preferably 1 to 7 kg/cm ² , and more preferably ² to 4.5 kg/cm ² . When the compressive strength is within this range, the above-mentioned appropriate cushioning property can be maintained for a long period of time.

Furthermore, the MD direction and TD of the plate-like foam 1 are
Bending average strength is preferably from 10 to 70 kg / cm ² in the direction, it is preferable that further 12~45kg / cm ^2. When the bending strength is within this range, the plate-shaped foamed body surely has the sufficient rigidity described above.

The thickness of the plate-like foam 1 is 2 to 7
It is preferably mm. When the thickness is in this range, it is easy to develop into a plate shape by the slitting method, and therefore the plate-shaped foam body is not curved and a flat one can be easily obtained.

In particular, in the present invention, the plate-like foam 1
Has a thickness of 2 to 7 mm and a density of 0.18 to 0.09 g/cm.
³ , the compressive strength is preferably 1 to 7 kg/cm ² , and the average bending strength in the MD direction and the TD direction is preferably 10 to 70 kg/cm ² . Such a plate-shaped foam 1 is excellent in punching workability, has both high rigidity and excellent cushioning property, and can maintain these physical properties for a long period of time.

In the present invention, the surface roughness (R) of the center line of JIS-B0601 (R
It is preferable that a) is 5 to 50 μm. When the surface roughness is in this range, the surface is relatively slippery, and therefore, when used as a packaging partitioning material or the like, the partitioning materials are unlikely to slide and the fitting state can be expected to be stable. Also, when used as a partitioning material for the bottom plate of a bag,
The effect that it is difficult to slip during sewing work can also be expected. In addition, in the plate-shaped foamed product of the present invention, a film, a non-woven fabric, a woven fabric, or the like can be stuck to improve the rigidity such as printing, surface hardness, and bending strength.

Since the plate-like foam of the present invention uses the non-crosslinked propylene resin as the base resin as described above, it is suitable for separation and recycling at the time of disposal. Therefore, the use of the plate-shaped foam of the present invention is economically advantageous, waste of resources can be eliminated, and the amount of waste can be reduced, which is effective in saving resources and protecting the environment.

Next, a method of manufacturing the polypropylene resin plate-like foam of the present invention will be described. 2 to 3 are conceptual views showing an example of a manufacturing process of the polypropylene-based resin plate-shaped foam of the present invention. The plate-shaped foam of the present invention, for example,
After melt-kneading the polypropylene-based resin and the foaming agent in the extruder, as shown in FIG. 2, the melt-kneaded product is attached to the tip of the extruder and an annular die having an annular lip is used. Extrusion foaming yields a tubular foam, then the tubular foam is cut open to form a sheet, and the sheet foam is wound up in a roll shape, and then, as shown in FIG. It is easily manufactured by adopting a method of drawing a sheet by heating and stretching it into a plate shape. It should be noted that the tubular foam may be cut open and formed into a sheet, and the sheet may be formed by heating and stretching as it is as shown in FIG. 3 without winding.

The step of obtaining the tubular foam will be described in more detail with reference to FIG. 2. An annular die 5 having an annular lip 4 is attached to the tip of the extruder 3 and extruded and foamed from the lip 4 of the die. To obtain a tubular foam body 6 as shown in the figure, and subsequently, to cool this tubular foam body 6 from the inside of a mandrel 7 whose inner surface is arranged inside the tubular foam body 6, The tube outer surface is cooled by a means such as blowing cooling air, and then the tubular foam 6 is cut open with a rotary blade 8 into a sheet shape, and the sheet foam 9 is wound into a winding roll 10 in a roll shape. deep. Reference numeral 11 is a mandrel support.

In the above, the diameter of the mandrel 7 can be appropriately selected according to the width of the plate-shaped foam 1 to be obtained.
The length of the mandrel 7 is arbitrary as long as it is long enough to cool and open the tubular foam 6. The extrusion speed (line speed) is slightly different depending on the length and diameter of the mandrel 7, but is preferably about 3 to 20 m/min. Further, the cooling temperature of the tubular foam 6 is preferably about 5 to 50° C., though it depends on the extrusion speed. The cooling means is not limited to the above-mentioned method and is arbitrary.
The wall thickness t of the tubular foam 6 is preferably 80 to 95% of the target thickness. Within this range, the production is easy, and the thickness of the finally obtained plate-like foam can be easily set within the preferable range of 2 to 7 mm.

In the present invention, a die having a specific extrusion condition and a specific structure was adopted at the stage of manufacturing the tubular foam 6. Specific extrusion conditions include, for example, an annular die attached to the tip of an extruder that is precisely temperature-controlled by oil temperature control to lower the temperature of the resin to a critical temperature at which crystallization does not occur, and an annular die that maintains a high viscosity. Is to pass through. The temperature controlled here is the temperature of the die, which is 3 more than the temperature of the breaker.
It is preferable to set the temperature lower by 10°C.

The die having a specific structure is, for example, a die having a structure in which the inside of the die undergoes rapid compression at the tip of the lip. Specifically, the structure is such that the pressure inside the die is less than 80 kg/cm ² .

By producing the tubular foam body 6 under the above-mentioned specific conditions, the bubbles have the specific shape of the present invention after passing the annular die 5 and before passing over the mandrel 7, and therefore the thickness is increased. In addition, after passing over the mandrel 7, the inner and outer surfaces of the tubular foam body 6 have both been completely cooled, so that the cell wall is surely solidified and the cell strength is improved. Then, the tubular foam 6 is cut out after passing through the mandrel 7 to obtain a sheet-like foam 9 having a large thickness and a high cell strength.
As a result, it becomes possible to easily obtain a foam having a relatively large thickness and a high rigidity as described later.

Unless the specific extrusion conditions and the specific die structure are adopted, the foam shape of the foam is A/B<0.4.
5, A/C<0.45, and only a thin sheet-like foam can be obtained, and a plate having sufficient rigidity even if the sheet-like foam is subjected to the processing described below. Foam is not obtained.

Next, the step of obtaining the plate-shaped foam 1 from the tubular foam 6 will be described in detail with reference to FIG. The sheet-shaped foam 9 of the winding roll 10 is fed to the feed roll 12,
It is drawn out through the space 12 and is further sent out to the drawing rolls 14, 14 through the space between the feed rolls 13 and 13. Between the feed rolls 12, 12 and 13, 13, for example, the heating furnace 1
The sheet-shaped foam 9 is heated by being passed through the sheet 5. During this heating, the bubbles inside the foam further expand, especially in the thickness direction, thereby increasing the thickness.
Since the sheet-shaped foam passed through the mandrel as described above and was obtained by the cut-open method, the difference in the orientation due to the difference in cooling on the front and back surfaces of the sheet-shaped foam and the thickness of the tubular foam. Due to the difference between the inner circumference and the outer circumference of the sheet-shaped foam, the sheet-shaped foam tends to bend. In order to completely eliminate the problems caused by these distortions, increase the temperature on the front and back surfaces of the sheet-like foam, such as strengthening the heating of the sheet-like foam surface that corresponds to the outer peripheral surface of the tubular foam. Is preferred.

The feed speed of the feed rolls 13 and 13 may be the same as or different from the feed speed of the feed rolls 12 and 12, but the former is usually faster. This is to correct the slack of the sheet-like foam that loosens during heating. Here, not only the slack is simply corrected, but some stretching may be performed as the slack is corrected.

Feed rolls 13, 13 and drawing rolls 14,
The feeding speed of the stretching rolls 14 and 14 is higher than that of the feeding rolls 13 and 13, and the sheet-shaped foam is formed between the feeding rolls 13 and 13 and the stretching rolls 14 and 14. 6 is stretched. It is assumed that the rolls do not slip with the foam sheet 6. At the time of stretching, the sheet-shaped foam 6 is heated, so that it is thermally stretched. By this stretching, the sheet-shaped foam 6 has increased rigidity and becomes a plate. At the same time, flare (waviness at the end in the width direction) and warpage are removed. The plate-shaped foam (plate-shaped foam 1) sent out through the stretching rolls 14, 14 is cut into a suitable size, for example, by a predetermined means (not shown) and stocked.

The processing conditions for heating and stretching the sheet-shaped foam 6 are appropriately selected depending on the thickness and density of the sheet-shaped foam 6, the kind of the base resin, etc.
The feed speed of 12 and 13, 13 is 3 to 15 m/min,
The feeding speed of the drawing rolls 14 and 14 is 3.5 to 17 m/m.
and the draw ratio is 1.05 to 1.3 times. The line speed is 3.5 to 17 m/min, which is the same as the feeding speed of the drawing rolls 14, 14.

Further, the feed rolls 12, 12 and 13, 13
The temperature of the heating performed between and is usually 150 to 23
It is 0°C. The heating means is not limited to radiant heating using the above-mentioned heating furnace 15 or the like, and various heating means such as contact heating using a heat roll or the like can be used.

The plate-like foam of the present invention has a single layer. However, this does not mean that it is not a plate-like foam made by a conventional laminating method and is not a laminate of sheet-like foams, and as described above, it is laminated with a film, a non-woven fabric, a woven fabric, or the like. Does not exclude anything.

In the case of the conventional bonding method,
Since the bonding is performed while the temperature of the inner surface of the balloon is high, the bubbles in the bonded part are crushed, and the closed cell ratio in that part is reduced, or as a result of the foaming agent gathering in that part, so-called voids are generated. Since the phenomenon occurs, it cannot be an excellent plate-shaped foamed body intended by the present invention. It is also difficult with this method to obtain a wide foam using a conventional extruder.

In contrast to the plate-like foam obtained by the above-mentioned bonding method, the plate-like foam of the present invention is manufactured by using the above-described method of cutting the tube-like foam on the mandrel, and therefore, it has a wide width (width is wide). (1000 mm or more) can be manufactured using conventional equipment, so there is no equipment cost, and since there is no need to drastically change extrusion molding conditions, manufacturing costs do not soar and are cheap. Advantageously, it can be provided.

[0064]

EXAMPLES The present invention will be described in more detail with reference to specific examples and comparative examples. Examples 1 to 5 After melt-kneading a base resin and a foaming agent in an extruder, the melt-kneaded product is extruded and foamed on a mandrel from an annular lip of a circular die having a special structure attached to the tip of the extruder to form a tubular shape. Then, the tubular foam was passed directly through the mandrel and cut open to obtain a sheet foam. Next, the obtained sheet-like foam,
Curls and flares were removed using a heating/stretching device having the structure shown in FIGS. Details are as follows (common to Examples 1 to 5).

[Base Resin] Ethylene-propylene block copolymer (SD632 manufactured by Highmont Co., Ltd.) MI: 3.1 (g/10 minutes) Crystallization temperature: 126 (° C.) Melting point: 158.3 (° C.) Melting Tension: 23 (g) Drawdown: 5 (m/min) [Foaming agent]-Butane [Foam regulator]-Mono sodium citrate [Extruder]-Tandem extruder [Compounding and temperature conditions]-Base resin The blending amounts of butane and monosodium citrate with respect to 100 parts by weight are shown in Table 1. The temperature conditions for extrusion foaming are also shown in Table 1. [Heating/stretching conditions]-Feeding speed of the feed rolls 12 and 5: 5 to 7 m/min-Gap between 〃〃 (sheet thickness x 0.7) mm-Feeding speed of the feed rolls 13 and 13 ~ 10% increase ・Gap between 〃 〃 (sheet thickness x 0.7) mm ・Distance between rolls 12, 12 and 13, 13 2-6m ・Feeding roll 14, 14 Feed speed 5 of roll 13 -30% increase ・Gap between 〃〃 (sheet thickness × 0.7) mm ・Line speed roll 13 speed increase by 5-30% ・Heating means Heating furnace ・Distance from heat source 0.1-0.2m ・Heating temperature (in heat source) 190-210°C

Comparative Examples 1 to 3 Using the same base resin, foaming agent and cell regulator as in Examples,
Extrusion foaming was performed under the compounding and temperature conditions shown in Table 1 with respect to 100 parts by weight of the base resin. In the extruder, a die having a conventional structure was used, and the tubular foam obtained by extrusion foaming was cut open to form a plate.

Comparative Example 4 A conventional plate-like foam obtained by the T-die method, which is a sample of another company's product.

Comparative Example 5 Using the same base resin, foaming agent and cell regulator as in Example,
Under the mixing conditions and temperature conditions shown in Table 1 with respect to 100 parts by weight of the base resin, the mixture was melt-kneaded in the extruder, and the melt-kneaded product was extruded into a tubular shape from an annular lip of a circular die attached to the tip of the extruder, and the die central part By supplying more air to form the foamed sheet into a balloon shape, while the inner surface of the balloon is not completely cooled and is in a bondable state, the balloon is sandwiched between the inner surfaces by a pressing roll to bond the inner surfaces to each other to form a thick foamed sheet. Obtained.

[0069]

[Table 1]

The thickness, width, density, compressive strength, bending strength, and surface roughness of the obtained plate-shaped foam or sheet-shaped foam were measured. The results are shown in Tables 2 and 3. Further, while observing the respective vertical cut surfaces in the MD direction and the TD direction, the average cell diameter A in the thickness direction and the average cell diameter B, T in the MD direction at the central portion in the thickness direction of each of the above cross sections.
The average bubble diameter C in the D direction was measured, and the ratio (A/B, A/C) of A to each of B and C was obtained (however, except for bubbles that are continuous bubbles, A and B are excluded. , C). This value is shown in Table 2. In addition, comprehensive evaluation was performed and is shown in Table 3. Observation of each cross section revealed that the bubbles in the central portion of the plate-shaped foams of Examples 1 to 5 satisfied the requirements of the present invention in their shape, and the bubble shapes in the surface layer portion other than the central portion were also almost the same. The cross sections in both the MD and TD directions were nearly circular. The bubbles in the center of Comparative Examples 1 to 3 had a flat shape that was short in the vertical direction and long in the horizontal direction. In addition, the foam shape of the central portion of the foam of Comparative Example 4 is an open cell as shown in FIG. 5 as a cross section in the thickness direction, and the foam shape in the vicinity of the central pressure bonding surface of Comparative Example 5 is flat or It was of open cells.

[0071]

[Table 2]

[0072]

[Table 3]

The value of [average cell diameter A in thickness direction]/[average cell diameter B in MD direction] is a microscopic enlarged photograph of a cross section in the thickness direction of the plate-like foam or sheet-like foam along the MD direction. Based on the obtained photographs, a line was drawn from both surfaces of the foam to a position corresponding to the position of 0.25T, and the cells were divided into a surface layer portion and a central portion, and there were 20 or more in the central portion. The diameter of each bubble in each direction is measured by a caliper as shown in FIG. 7 to obtain the values of a and b of each bubble for each bubble. The values of a ₁ , a ₂ , a ₃ ... _n ,
Also, the arithmetic mean values A and B are obtained from the values of b ₁ , b ₂ , b ₃ ... b _n , respectively, and A/B is obtained from the values of A and B.
Got the value of. It should be noted that the values of A and B may be converted based on the enlargement ratios of the above photographs, but this is not necessary because they are eventually reduced when calculating A/B. still,
Bubbles on the 0.25T line from both surface layers were excluded from the measurement.

The value of [average cell diameter A in thickness direction]/[average cell diameter C in TD direction] is a microscopic enlarged photograph of a cross section in the thickness direction of the plate-like foam or sheet-like foam along the TD direction. Based on the obtained photographs, a line was drawn from both surfaces of the foam to a position corresponding to the position of 0.25T, and the cells were divided into a surface layer portion and a central portion, and there were 20 or more in the central portion. The diameter of each bubble in each direction is measured with a caliper as shown in FIG. 7 to obtain the values of a and c of each bubble for each bubble. The values of a ₁ , a ₂ , a ₃ ... _n ,
And the arithmetic mean values A and C are obtained from the values of c ₁ , c ₂ , c ₃ ... C _n , and A/C is obtained from the values of A and C.
Got the value of. It should be noted that the values of A and C may be converted based on the enlargement ratio of the above-mentioned photograph, respectively.
When calculating A/C, it is not necessary because it is eventually reduced. Bubbles on the 0.25T line from both surface layers were excluded from the measurement.

With respect to the compressive strength, a universal tester [Tensilon manufactured by Orientec Co., Ltd.] was used to stack test pieces in a length of 50 mm×width of 50 mm×thickness of about 25 mm, and the thickness was 10 mm/min at 10 mm/min. % Compression, and the stress at that time was measured.

The bending strength was measured by a universal testing machine [Tensilon manufactured by Orientec Co., Ltd.] according to JIS-K7203, with a test piece width of 25 mm, a distance between fulcrums of 50 mm, and a test speed of 10 mm/min.

The center line surface roughness (Ra) was measured with a surface roughness measuring device (SE-30D manufactured by Kosaka Laboratory Ltd.) according to JIS-B0.
In accordance with 601 (measurement condition: feed rate 0.1 mm/s
ec, reference length 8 mm, cutoff value λc=2.5).

The drawdown property was measured by using a melt tension tester type II manufactured by Toyo Seiki Seisaku-sho, increasing the winding speed of the winding machine using the apparatus shown in FIG. 6 under the following measurement conditions, and cutting the string-like resin. The winding speed at that time was obtained. Measurement temperature: 230° C. Piston pressing speed: 10 mm/min Cylinder diameter: 9.55 mm Cylinder length: 162 mm Nozzle diameter: 2.095 mm Nozzle length: 8.00 mm Piston diameter: 9.474 mm Piston length: 6.35 mm

The melt tension is measured by the same apparatus and measurement conditions as those for the drawdown property measurement, the winding speed at which the melt tension shows a steady state is determined, and the average of the melt tension at the steady state is obtained. Adopted the value.

Test Example The plate-like foams of the present invention obtained in Examples 1 to 5 and the conventional plate-like foam of Comparative Example 4 were punched to form a double cross as shown in FIG. 200 pieces of partitioning materials (indicated by reference numeral 16 in FIG. 4) that can be assembled were manufactured. As shown in the figure, the specifications of the partition member 16 are as follows: total length L=315 mm, total width W=130 mm, groove 17
The width w was 4 mm, the length h of the groove 17 was 70 mm, and the pitch p of the groove 17 was 75 mm. It should be noted that this specification is an example for testing, and the partition material of the present invention is not limited to the above-mentioned shape and size specifications. In manufacturing this partition material, its punching workability was evaluated. The evaluation was carried out for each evaluation item shown in Table 4 based on the evaluation criteria shown in the same table, and the evaluation results for each item were evaluated based on the criteria shown in the table, and thus the comprehensive evaluation was made. The results are also shown in Table 4.

[0081]

[Table 4]

As shown in Tables 2 and 3, the plate-like foam of the present invention has a cell shape standing vertically as compared with the conventional sheet-like foam having a relatively large thickness, and has a compressive strength and a bending strength. It is strong and has sufficient rigidity as a plate.
Further, the surface roughness is rougher than that of the conventional plate-like foam.

As shown in Table 4, the plate-like foam of the present invention is superior in punching workability to the conventional plate-like foam.

[0084]

[However, in the conditional expression, A is the average cell diameter in the foam thickness direction, B is the average cell diameter in the foam extrusion direction (MD direction), and C is the direction orthogonal to both the foam extrusion direction and the thickness direction (TD Direction) average bubble diameter)

By using the polypropylene-based resin plate-like foam of the present invention, it is possible to accurately process into a desired size and shape at a low cost. And excellent durability, for example, a curing sheet used for moving, etc., various packaging materials such as partitioning materials, or various materials such as packing materials of metal materials such as aluminum sashes can be provided at low cost. ..

Further, in the above plate-shaped foam, the thickness 2
-7 mm, density 0.18-0.09 g/cm ³ , compressive strength 1-7 kg/cm ² , and punching workability when the average of bending strength in MD and TD is 10-70 kg/cm ² . In addition to being excellent in high rigidity and excellent shock absorbing property, it is possible to maintain the above high rigidity and excellent shock absorbing property for a long period of time. Therefore, when it is processed into a curing sheet or a partition material and used, even if it is processed into a shape in which the strength tends to be relatively weak, sufficient rigidity can be obtained as a whole, so that the degree of freedom of the processed shape can be expanded. Produce an effect.

Further, in the above-mentioned plate-like foam, when the surface roughness represented by the center line average roughness (Ra) is 5 to 50 μm, the surface is relatively slippery, and therefore, as a packaging partitioning material or the like. When it is used, since the partition members are not loosely fitted to each other and the partition interval can be maintained, the problem that the package object is easily deviated and damaged due to the increased interval is not caused. Further, since the object to be packaged does not slide due to friction with the partition material, it is possible to expect an effect that it is difficult for the partition material to move between the partition materials and the posture is stable. Further, when used as a bottom plate of a bag, etc., it is difficult to slip, so that it has an effect of facilitating the sewing process.

Further, the partitioning member made of the above-mentioned plate-like foam body supports the article to be packaged flexibly, and prevents the article to be delusionally moved, thus damaging the article to be packaged. Without being hampered, the product to be packaged can be reliably protected when used for transportation or storage.

[Brief description of drawings]

FIG. 1 is a schematic view showing a vertical section of a polypropylene-based resin plate-like foam of the present invention.

FIG. 2 is a conceptual diagram showing a part of the manufacturing process of the polypropylene-based resin plate-shaped foam of the present invention.

FIG. 3 is a conceptual diagram showing a part of the manufacturing process of the polypropylene-based resin plate-shaped foam of the present invention.

FIG. 4 is a diagram showing an application example of the polypropylene-based resin plate-shaped foam of the present invention.

FIG. 5 is a schematic view showing a vertical cross section of a conventional polypropylene-based plate-shaped foamed product obtained by a T-die method.

FIG. 6 is an explanatory view of an apparatus for measuring drawdown property.

FIG. 7 is a diagram for explaining the meaning of bubble diameter in the present invention.

[Explanation of symbols]

1 Polypropylene-based resin plate-shaped foam 2 Air bubbles 16 Middle partition material made of polypropylene-based resin plate-shaped foam

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akinori Hira 1078-4 Komagaicho, Utsunomiya City, Tochigi Prefecture Casa Ai 202

Claims (4)

[Claims] 1. A single-layer plate-like foam having a density of 0.3.
˜0.06 g/cm ³ , and the shape of the bubbles present inside both the surfaces of the foam in the thickness direction cross section of the foam exceeding 25% of each thickness satisfy the following conditional expressions (1) and (2). Polypropylene resin plate-like foam characterized by the following. 0.45 ≤ A/B ≤ 1.0 (1) 0.45 ≤ A/C ≤ 1.0 (2) [However, conditions In the formula, A is the average cell diameter in the thickness direction of the foam, B
Is the average cell diameter in the foam extrusion direction (MD direction), and C is the average cell diameter in the direction (TD direction) perpendicular to both the foam extrusion direction and the thickness direction] 2. A thickness of 2 to 7 mm and a density of 0.18 to 0.0
9 g/cm ³ , compressive strength 1 to 7 kg/cm ² , average bending strength in MD and TD directions is 10 to 70 kg/cm
The polypropylene-based resin plate-shaped foam according to claim 1, which is ² . 3. The polypropylene-based resin plate foam according to claim 1, which has a surface roughness represented by a center line average roughness (Ra) of 5 to 50 μm. 4. A partitioning member made of the polypropylene-based resin plate foam according to claim 1.