Resin composition for concrete form panels, and form panel

Abstract

To provide a resin composition for concrete form panels capable of solving the problems such that in construction using concrete, plywood panels which are lightweight and capable of sawing and nailing are frequently used from points of handling and it is difficult to reuse them multiple times, so they are incinerated, thus, there are strong demands for form panels and compositions having handling properties equivalent to those of as plywood panels, capable of repeated use and having recyclability in view of CO2 reduction and SDGs.SOLUTION: Two specific types of polypropylene (homopolypropylene with an MFR of a certain value or lower and block polypropylene with high impact strength) are combined in a certain ratio and are composited with a bio-filler and an inorganic filler, and if necessary, an interfacial modifier or a melt tension improver may be used in combination in a certain ratio. With this, a lightweight form panel that can be used repeatedly and has recyclability, and a composition can be obtained.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a resin composition for a concrete form panel, which contains a biomass filler and a polypropylene resin as main components, and a form panel produced using the resin composition. [Background technology]

[0002] When constructing a concrete building, concrete formwork panels are essential materials, and currently, plywood made from imported wood is used. However, after using these wooden formwork panels 2-3 times, they become difficult to use any more due to the adhesion of cement and damage caused by the impact when peeling them off. Currently, unusable wooden formwork panels are transported to incinerators and incinerated. There is a strong demand for reducing CO2 emissions from the perspective of protecting the global environment, and it has become important to develop a concrete formwork panel that can replace plywood in line with the ideas of the SDGs. A formwork panel that meets this requirement should be reusable 10-15 times or more, and should be recyclable and remade into a formwork panel after use. Formwork panels made of polypropylene resin or its composite materials have been proposed as an alternative to wooden formwork panels, but there are many other characteristics required of formwork panels in addition to recyclability, and the reality is that no formwork panel meets these requirements.

[0003] The characteristics required for form panels are: (1) they must be a large product, but light enough to be carried by one person; (2) they must be rigid enough to withstand the weight of concrete; (3) they must have impact strength to withstand the impact when removing the form panels; (4) they must be able to be sawed in the same way as wood; (4) they must be able to be nailed and have the ability to hold nails; (5) they must have a smooth surface; (6) they must have minimal adhesion of concrete; (7) they must be able to be used repeatedly 10 to 15 times or more; and (8) they must be recyclable and turned back into form panels.

[0004] Although there are several prior patent documents relating to resin concrete formwork panels, none of them satisfy all of the various required characteristics. In particular, there has been a strong demand for formwork panels and materials (compositions) therefor that have handleability (lightweight, sawing ability, nailing ability) and reusability (reusability and impact resistance therefor) equal to or greater than that of the widely used plywood.

[0005] Patent Document 1 discloses a "concrete formwork panel with a specific gravity of 0.8 or less, which is manufactured by adding 0.4% by mass or more of a foaming agent to 100% by mass of a molding material consisting of 46-52% by mass of thermoplastic resin mainly composed of polypropylene, 33-38% by mass of wood flour with an average particle size of 50-300 μm, and the remainder as secondary materials, and extruding the mixture." However, since no consideration was given to repeated use or recycling to return the panel to a concrete formwork panel, there were problems such as low impact strength and breakage when the panel was removed. Furthermore, since no melt tension improver was used, the range in which wood flour and the like can be used was very narrow and limited, and there were problems such as recycling being very difficult. Patent Document 2 discloses a "high-strength panel using a polypropylene composition containing 10 to 60% by weight of paper powder and / or wood powder and 0 to 40% by weight of talc powder." However, What is disclosed is simply an extruded concrete panel, which is difficult to saw and nail and is therefore technically different from lightweight extruded foam concrete panels. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2019-130861 A [Patent Document 2] Japanese Patent Application Publication No. 07-108582 Summary of the Invention [Problem to be solved by the invention]

[0007] The problem to be solved is to find a form panel and a material (composition) for it that has handling properties (lightness, sawing ability, nailing ability) equivalent to those of plywood concrete form panels, and that is far superior to plywood in terms of repeated use and recyclability in accordance with the ideas of the SDGs. [Means for solving the problem]

[0008] The present invention relates to a resin composition for concrete formwork panels, which comprises 40-70 wt% of a polypropylene resin mixture, in which (A) a homopolypropylene resin having a melt flow rate (MFR) of 5.0 or less and (B) a block polypropylene resin having a Charpy impact strength of 10 KJ / m2 or more, and the ratio of these is B / (A+B)=0.2-0.8, 10-50 wt% of a biomass filler, and 0-40 wt% of an inorganic filler. The inventors have found that the object can be achieved by combining two specific types of polypropylene in a certain ratio and compounding the biofiller with the inorganic filler, and further combining and using an interface modifier and a melt tension improver in a certain ratio.

[0009] As the homopolypropylene resin (A) in the present invention, a commercially available homopolypropylene resin can be used, but it is necessary that the MFR is not more than 5.0. If the MFR is more than 5.0, the melt tension of the resin composition is insufficient, and gas is scattered during foaming of the resin composition, resulting in insufficient foaming or the formation of voids inside the molded product, making it difficult to achieve uniform foaming.

[0010] In the present invention, the block polypropylene (B) has a Charpy impact strength of 10 KJ / m2 or more. If the notched Charpy impact strength is less than 10 KJ / m2, the impact strength of the composition is insufficient, and when the concrete formwork panel is removed from the concrete with a crowbar for repeated use, the panel is broken by the impact and cannot be used sufficiently repeatedly.

[0011] The ratio of (A) and (B) is limited, and it is preferable that B / (A+B) is 0.2 to 0.8. If it is less than 0.2, the impact strength is insufficient, and it becomes difficult to use the form panel repeatedly. If it is more than 0.8, the product rigidity is insufficient, and it becomes difficult to use it as a form panel.

[0012] The proportion of the polypropylene resin mixture consisting of (A) and (B) in the resin composition is 40 to 70 wt%. If the proportion of the polypropylene resin mixture is less than 40 wt%, not only is it difficult to sufficiently foam the resin composition, but the impact resistance strength of the formwork panel is reduced, making it difficult to repeatedly use the panel. If the proportion of the polypropylene resin mixture exceeds 70 wt%, the rigidity of the formwork panel is insufficient, making it impossible to use the formwork panel.

[0013] Examples of biomass fillers include wood powder, bamboo powder, cellulose powder, etc., and their average particle size is 30 to 500 μm, preferably 50 to 400 μm. The ratio of the biomass filler to the resin composition for concrete formwork panels is 10 wt% to 50 wt%. If it is less than 10 wt%, the rigidity of the formwork panel is insufficient, and if it exceeds 50 wt%, it becomes difficult to uniformly foam the formwork panel and the impact strength decreases, making it difficult to repeatedly use the formwork panel.

[0014] Examples of inorganic fillers include mica, talc, sericite, glass flakes, graphite, kaolin, calcium carbonate, silica, titanium oxide, alumina, magnesium hydroxide, aluminum hydroxide, barium sulfate, wollastonite, glass fiber, potassium titanate fiber, magnesium oxysulfate, etc., among which talc and mica are preferred, and their ratio in the resin composition for concrete formwork panels is 0 to 40 wt%. If it exceeds 40 wt%, it becomes difficult to achieve uniform foaming and the impact strength of the concrete formwork panel decreases, making repeated use difficult.

[0015] Acid-modified polypropylene is a polypropylene molecule into which an unsaturated carboxylic acid has been introduced. Examples of unsaturated carboxylic acids include acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, crotonic acid, and sorbic acid. Examples of derivatives of the unsaturated carboxylic acids include acid anhydrides, esters, amides, imides, and metal salts. Examples of the derivatives of the unsaturated carboxylic acids include maleic anhydride, itaconic anhydride, methyl acrylate, methyl methacrylate, ethyl acrylate, butyl acrylate, acrylamide, maleic acid monoamide, and maleimide. Among these, unsaturated dicarboxylic acids and their derivatives are preferred, and maleic acid is particularly preferred. The amount of the additive is 0.5 to 3 parts by weight per 100 parts by weight of the resin composition for concrete formwork panels. If the amount is less than 0.5 parts by weight, the interface between the resin and the biomass filler is not sufficiently modified, and the effect of suppressing gas scattering and promoting uniform foaming, as well as the effect of improving the strength and rigidity of the formwork panel, are insufficient. If the amount of the additive exceeds 3 parts by weight, the interface improvement effect is saturated, and no further effect is expected, which is economically disadvantageous.

[0016] The melt tension improver is, for example, acrylic modified PTFE, acrylic resin, long chain branched polyolefin resin, etc. The amount used is 0.1 to 5 parts by weight per 100 parts by weight of the resin composition for concrete formwork panels. If it is less than 0.1 parts by weight, the effect of improving melt tension is small and the effect of improving foaming is insufficient. If it exceeds 5 parts by weight, the melt tension and viscosity increase too much, making it difficult to extrude and, conversely, making it difficult for the resin to expand, and therefore making it difficult to foam.

[0017] To reduce the weight of the form panels, they need to be foamed, and the foaming method is the usual polypropylene extrusion foaming method. Among them, the Cerca method is preferred. The foaming ratio is preferably 1.3 to 2.0 times. If it is less than 1.3 times, the nailing characteristics will not be satisfactory and it will be difficult to maintain the smoothness of the product surface. In addition, the product will be too heavy and difficult to use. If it is more than 2.0 times, voids will easily form inside the molded product, making it difficult to foam uniformly. As a result, the nails will easily come out and the form panels will be easily broken when peeled off from the concrete, making repeated use of the form panels difficult. In addition, the rigidity of the product will decrease. Effect of the Invention

[0018] By using the resin composition of the present invention, the above problems can be solved. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] The objective was achieved by combining a specific homopolypropylene resin, a specific block polypropylene resin, a biomass filler and an inorganic filler. EXAMPLES

[0020] Table 1 shows the composition used in this experiment. There are four types of homopolypropylene with MFR=0.5, 1.9, 3.0, and 10; there are three types of block polypropylene with Charpy impact strength of 7.5, 33, and 50KJ / m2; there are biomass fillers such as wood powder (200μ), cellulose powder (80μ), and bamboo powder (300μ); there is inorganic filler such as talc (5μ); acid-modified polypropylene (1) is maleic acid grafted polypropylene, and acid-modified polypropylene (2) is acrylic acid grafted polypropylene; melt tension improver (1) is Metabrene A-3000 (manufactured by Mitsubishi Chemical: acrylic modified PTFE), and melt tension improver (2) is Metabrene P-1050 (manufactured by Mitsubishi Chemical: acrylic modifier).

[0021] The components shown in Table 1 were dry blended, then kneaded using a twin-screw kneader to produce pellets for extrusion. The pellets obtained were then dried at 110°C for 24 hours, after which a foaming agent was dry blended and extrusion foam molding was used to produce concrete formwork panels (concrete panels) with a thickness of 12 mm, width of 600 mm and length of 1800 mm, which were then evaluated as formwork panels. The foaming agent used was Polythrene EE515 (manufactured by Eiwa Chemical Industry Co., Ltd.), a master batch of sodium bicarbonate, blended at 2 wt%. The evaluation results are shown in Table 2.

[0022] Formwork panel molded product 1 and formwork panel molded product 2 were produced using the compositions of Example 1 and Example 2, respectively. The formwork panels produced by extrusion foam molding were uniformly foamed and satisfied all of the required performance characteristics, such as surface smoothness, nailing performance, and product rigidity. In addition, the formwork was peeled off with a crowbar and used repeatedly more than 10 times without any problems.

[0023] Formwork panel molded product 3 was made using the composition of Comparative Example 1, which does not contain block polypropylene. When the formwork panel was peeled off from the concrete with a crowbar and used repeatedly, it broke after three tries. This shows that block polypropylene with high impact resistance is essential for repeated use.

[0024] Formwork panel molded product 4 was made using the composition of Comparative Example 2, which contains less homopolypropylene than the range of the claims. The product lacked rigidity and could not withstand the pressure of concrete, so it was judged difficult to use as a formwork. This shows that a certain proportion of homopolypropylene with a high elastic modulus is necessary. There was also a problem that voids were generated inside the molded product due to insufficient melt tension, which caused nails driven into the formwork panel to easily come out.

[0025] Formwork panel molded product 5 was made using the composition of Comparative Example 3, in which the MFR of the homopolypropylene was greater than the range of the claims, and the melt tension was low, causing gas to escape, and a satisfactory foam molded product was not obtained. As a result, the molded product was heavy, had sink marks on the surface, and was not smooth enough, and it was determined that it was difficult to use as a formwork panel.

[0026] Next, the compositions of Example 3 and Comparative Example 4 were used to carry out extrusion foam molding of the above-mentioned concrete formwork panels. The amount of foaming agent added was changed to examine the effect of the foaming ratio. The evaluation results are shown in Table 3. Formwork panel molded product 6 was obtained by adding 1.5 parts by weight of foaming agent to the composition of Example 3, and had a foaming ratio of 1.4 times. The inside of the molded product was foamed uniformly, satisfying all the required performance as a formwork panel, and there was no problem at all even when the formwork panel was peeled off from the concrete with a crowbar and used repeatedly more than 10 times.

[0027] The molded panel product 7 was obtained by adding 0.5 parts by weight of a foaming agent to the composition of Example 3, and had an expansion ratio of 1.1 times. Although there were no voids, the foaming was insufficient. Therefore, it was difficult to drive nails into the molded product, and the surface of the molded product was not smooth, making it difficult to use as a molded panel. The molded panel product 8 was obtained by adding 5 parts by weight of a foaming agent to the composition of Example 3, and had an expansion ratio of 2.8 times. Large voids were found inside the molded product. Therefore, a problem occurred in which the nails driven into the molded panel easily came out. The rigidity of the product also decreased. In addition, when peeling off the molded panel with a crowbar in a repeated test, it broke after two tries. This is thought to be due to the large voids inside. These results show that it is important to keep the expansion ratio within the range of the claims.

[0028] The molded panel product 9 was obtained by adding 1.5 parts by weight of a foaming agent to the composition of Comparative Example 4, and had an expansion ratio of 1.05 times. The foaming gas escaped, and a sufficient foamed molded product was not obtained. As a result, it was heavy, difficult to nail, had sink marks on the surface, and was insufficient in smoothness, making it difficult to use as a molded panel.

[0029] Formwork molded product 10 was obtained by adding 5 parts by weight of the foaming agent to the composition of Comparative Example 4. The foaming ratio was 1.2 times. Even if the foaming agent was increased, the foaming gas escaped, and a sufficient foamed molded product was not obtained. There were also voids inside the molded product. Therefore, the smoothness of the molded product surface was not sufficient. In addition, when peeling off the formwork panel with a crowbar in a repeated test, it broke after two tries. This is thought to be because the proportion of polypropylene was less than the claimed range and the amount of biomass filler exceeded the claimed range. These results show that it is difficult to obtain the desired foamed molded product of a concrete formwork panel even if the amount of foaming agent is adjusted for a composition that deviates from the claimed range, and even if it can be molded, it is not possible to satisfy all the properties required for the formwork panel.

[0030] [Table 1]

[0031] [Table 2]

[0032] [Table 3]

Claims

1. A resin composition for concrete formwork panels, comprising 40-70wt% of a polypropylene resin mixture consisting of (A) homopolypropylene with an MFR of 5.0 or less and (B) block polypropylene with a notched Charpy impact strength of 10KJ / m2 or more, with the ratio B / (A+B) being 0.2-0.8, 10-50wt% of a biomass filler, and 0-40wt% of an inorganic filler.

2. A resin composition for a concrete form panel, comprising 100 parts by weight of the resin composition according to claim 1 and 0.5 to 3 parts by weight of an acid-modified polypropylene.

3. A resin composition for concrete form panels, comprising 0.1 to 5 parts by weight of a melt tension improver added to 100 parts by weight of the resin composition according to claim 1 or 2.

4. A concrete form panel produced by extruding and foaming the resin composition according to claim 1, 2 or 3 to an expansion ratio of 1.3 to 2.0.

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