Polypropylene resin composition, wood-resin bonded body using the same, and method for producing the same

Abstract

To provide a polypropylene resin composition for joined to a wood surface which enables formation of a wood resin joined body having sufficient joint strength without destructing wood, and a wood resin joined body using the same and a method for manufacturing the same.SOLUTION: A polypropylene resin composition for joined to a wood surface has a gap derived from a conduit, a tracheid or an artificial aperture part, in which the polypropylene resin composition contains a polypropylene resin and polyolefin having a number average molecular weight (Mn) of 1,000 to 40,000, and the polypropylene resin has one or more characteristics of the following characteristics (1) to (3). Characteristic (1): an ethylene content of 0.8-10 mass%. Characteristic (2): a crystallization initiation temperature by differential scanning calorimetry (DSC) of 80-110°C. Characteristic (3): a number average molecular weight (Mn) of 40,000 to 100,000.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a polypropylene resin composition for bonding to a wood surface, a wood-resin joined body using the same, and a method for producing the same. More specifically, the present invention relates to a polypropylene resin composition that exhibits sufficient joining strength, a wood-resin joined body using the same, and a method for producing the same. [Background technology]

[0002] In modern times, materials such as resin, iron, and concrete have appeared and are now widely used in place of wood. However, in recent years, various technologies have been developed to overcome the drawbacks of wood, and the use of wood is once again attracting attention.

[0003] Wood materials are very lightweight compared to resin materials of the same strength, but they have the disadvantage of being difficult to process as easily as resin. In particular, curved shapes with small radii of curvature cannot be created as easily as with resin, and wood materials are generally created by carving. Of course, it is possible to process wood into curved shapes by applying heat, but even so, it is difficult to create curves with small radii of curvature beyond gentle curves with a tensile strain of 1-2% or less.

[0004] One way to solve the problem of the difficulty of processing to create curved shapes, for example when manufacturing a mobile phone case, is to use thin wood for the flat parts and resin for the curved parts, joints, and parts that require complex shapes such as latches, and then glue them together. However, even with the use of adhesives or compatibilizers, the adhesive strength is not sufficient, making this a component that lacks practicality.

[0005] In order to solve the problem of joining wood and resin, Patent Document 1 proposes a resin-bonded thin wood plate in which resin is bonded to the side of the thin wood plate, and the resin penetrates into the countless voids that extend from the side of the thin wood plate into the interior of the wood; and a method for manufacturing such a bonded thin wood plate, in which the thin wood plate is placed in a mold so that both the front and back surfaces are in close contact with the mold, and then resin is injected into the mold or a liquid molding material is poured in, and the resin is bonded to the thin wood plate while being molded. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2020-124911 Summary of the Invention [Problem to be solved by the invention]

[0007] In the manufacturing method of resin-bonded wood sheets described in Patent Document 1, if the injection pressure is too high, the wood sheets may not be able to withstand the resin pressure and may split. Also, if the resin temperature is increased to increase the resin fluidity, the wood sheets may burn or scorch.

[0008] An object of the present invention is to provide a polypropylene resin composition for bonding to a wood surface, which can form a wood-resin bonded body having sufficient bonding strength without destroying the wood, a wood-resin bonded body using the same, and a method for producing the same. [Means for solving the problem]

[0009] As a result of extensive investigations to achieve the above object, the present inventors have discovered that a polypropylene resin composition containing a polypropylene resin having predetermined properties and a low-molecular-weight polyolefin can penetrate into voids on the surface of wood without destroying the wood, thereby forming a wood-resin joined body having sufficient joining strength, and have arrived at the present invention.

[0010] The present invention relates to the following [1] to [8]. [1] A polypropylene resin composition for bonding to a wood surface having voids derived from vessels, tracheids or artificial openings, the polypropylene resin composition comprising a polypropylene resin and a polyolefin having a number average molecular weight (Mn) of 1,000 to 40,000, the polypropylene resin having one or more of the following properties (1) to (3): Property (1): The ethylene content is 0.8 to 10% by mass. Property (2): The crystallization onset temperature measured by differential scanning calorimetry (DSC) is 80 to 110°C. Property (3): Number average molecular weight (Mn) is more than 40,000 to 100,000. [2] The polypropylene resin composition according to [1], wherein the polypropylene resin has the following property (4): Property (4): The crystallization temperature measured by differential scanning calorimetry (DSC) is 79 to 109°C. [3] The polypropylene resin composition according to [1] or [2], wherein the polypropylene resin has the following property (5): Property (5): The difference between the crystallization onset temperature and the crystallization temperature is 1 to 6°C. [4] The polypropylene resin composition according to any one of [1] to [3], wherein the polypropylene resin has the following property (6): Property (6): Mw / Mn is 2.0 to 4.0. (Mn is the number average molecular weight, and Mw is the weight average molecular weight.) [5] The polypropylene resin composition according to any one of [1] to [4], further comprising a modified polyolefin. [6] The polypropylene resin composition according to any one of [1] to [5], further comprising a filler. [7] A wood-resin joined body of wood and the polypropylene resin composition according to any one of [1] to [6], wherein the polypropylene resin composition penetrates into the voids on the surface of the wood. [8] A method for producing a wood-resin joined body according to [7], comprising the steps of placing wood in a mold cavity and injecting a plasticized resin composition into the mold. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a polypropylene resin composition for bonding to a wood surface, which can form a wood-resin bonded body having sufficient bonding strength without destroying the wood, a wood-resin bonded body using the same, and a method for producing the same. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram of a resin-bonded thin wood plate assembly produced in the example. [Figure 2] FIG. 2 is an X-ray CT image of the joint of the resin-bonded thin wood plates produced in Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0013] The polypropylene resin composition of the present invention is a polypropylene resin composition for bonding to a wood surface having voids derived from vessels, tracheids or artificial openings, and the polypropylene resin composition contains a polypropylene resin and a polyolefin having a number average molecular weight (Mn) of 1,000 to 40,000 (hereinafter also referred to as a low-molecular-weight polyolefin), and the polypropylene resin has one or more of the following properties (1) to (3): Property (1): The ethylene content is 0.8 to 10% by mass. Property (2): The crystallization onset temperature measured by differential scanning calorimetry (DSC) is 80 to 110°C. Property (3): Number average molecular weight (Mn) is more than 40,000 to 100,000. By using a polypropylene resin composition containing a polypropylene resin having one or more of the above properties (1) to (3) and a low-molecular-weight polyolefin, a wood-resin joined product having sufficient bonding strength can be obtained without destroying the wood. Because the wood-resin joined product of the present invention has sufficient bonding strength, the amount of adhesive or compatibilizer used can be reduced or eliminated, making it possible to use it as an environmentally friendly material.

[0014] [wood] The wood used in the present invention includes all wood materials that have micro- and macro-voids due to tracheids and vessels, such as solid wood, wood materials made by laminating boards together, fiberboards with no clear fiber orientation, and particle boards. The tree species is not limited. Examples of tree species that can be used include cypress, cedar, larch, Douglas fir, spruce, hemlock, cedar lamina, oak, paulownia, zelkova, maple, horse chestnut, beech, cherry, teak, lauan, and spinal.

[0015] In the case of wood materials made by laminating and bonding boards, the direction of the wood fibers may be aligned as in solid wood and LVL (Laminated Veneer Lumber), or may be perpendicular as in plywood. The shape of the wood is not particularly limited, and may be, for example, a thin plate, a board, a prism, a cylinder, a pyramid, a cone, or an irregular shape. The shape of the joints in wood is typically flat, but may also be any shape, such as stepped, tenon-shaped, jagged, curved, or irregular.

[0016] In the case of thin or plank-shaped wood, the surface is typically rectangular, but the shape may be circular, oval, triangular, trapezoidal or other polygonal, or irregular, and is not particularly limited. Furthermore, thin or plank-shaped wood is wood that is thin compared to its length and width if its surface is rectangular, and is typically a flat board, but the flat board may have curved portions.

[0017] As the wood, for example, a thin-layered wood multilayer molded product (Micro Multiple Plywood, hereinafter referred to as MMP) disclosed in Japanese Patent Application Laid-Open No. 2013-226680 can be used. MMP is a thin plate with a thickness of 2 mm or less, made by stacking 5 to 20 layers of ultra-thin boards with a thickness of 0.3 mm or less, with the fibers aligned perpendicular to each other. It is a lightweight and strong thin plate, with the total mass of adhesive used to bond the ultra-thin boards being 40% or less of the total mass of the ultra-thin boards. The use of MMP is advantageous because it is less susceptible to dimensional changes due to heating during bonding with a polypropylene resin composition, and to dimensional changes due to moisture absorption after bonding.

[0018] The surface of the wood to which the polypropylene resin composition is bonded has voids derived from vessels, tracheids or artificial openings. Typically, there are numerous voids, like rows of pipe holes, on the surface perpendicular to the grain direction of wood. These voids correspond mainly to tracheids in conifers and mainly to vessels in hardwoods, and extend like pipes from the joint to the interior of the wood in the grain direction. Furthermore, in wood that does not have a clear grain orientation, these voids appear randomly. Penetrating these numerous voids with resin by injection molding or the like creates an anchor effect, making it possible to bond wood and a polypropylene resin composition with sufficient bonding strength. Penetration means that the resin composition enters the voids. When the resin composition flows into the voids extending from the joint into the wood and hardens or solidifies, the hardened or solidified resin composition enters the voids and forms a shape resembling multiple rows of spikes or multiple pins.

[0019] To maximize the anchor effect and obtain higher joint strength, it is preferable to use wood with a clear grain direction, and if the grain direction is aligned, it is more preferable to join in the same direction as the grain direction of the wood, and if it is perpendicular, it is more preferable to join in the same direction as the grain direction of one of the stacked boards. However, in this case, the joining direction does not have to strictly match the grain direction.

[0020] Naturally, resin compositions cannot penetrate the edges of solid wood and laminated veneer lumber (LVL), which do not have voids extending into the wood due to tracheids or vessels, and therefore cannot be bonded with sufficient bond strength. Therefore, using MMP or plywood allows the resin composition to be bonded to all sides, greatly expanding the range of uses for wood-resin composites. However, it is acceptable for solid wood and LVL, which do not have voids extending into the wood, to become part of the wood's components.

[0021] The surface of the wood may be provided with voids derived from artificial openings other than vessels or tracheids. The artificial openings may be through holes extending from one surface to the other, or blind holes extending partway through the interior of the wood. By forming artificial openings, the resin composition penetrates the artificial openings, creating a stronger anchoring effect and thereby increasing the strength of the wood-resin joined body. Furthermore, when only vessel or tracheid-derived voids are present, the joining strength of the wood-resin joined body is likely to vary depending on the type of wood and individual differences. However, by forming artificial openings, this variation can be reduced.

[0022] There are no particular restrictions on the number, arrangement, shape, and direction of the artificial openings as they extend into the wood, but it is preferable to consider the number, arrangement, shape, and direction so as to increase the bonding strength between the wood and resin while suppressing a decrease in the strength of the wood itself in which the openings are formed, and to balance the strength of both.

[0023] From the viewpoint of achieving sufficient joint strength without destroying the wood, it is preferable that the arrangement of the artificial openings is uniform throughout the joint, without being biased towards a specific location in the joint.

[0024] The shape of the artificial opening is not particularly limited. For example, the cross section of the opening may be circular, elliptical, polygonal such as triangular or rectangular, or irregular, but is preferably circular because it is easy to set up the opening.

[0025] From the viewpoint of achieving sufficient bonding strength without destroying the wood, the cross-sectional area of ​​the artificial openings is preferably 0.001 to 1 mm, more preferably 0.01 to 0.1 mm, in terms of circle equivalent diameter. The cross-sectional area of ​​the openings may remain constant in the depth direction from the surface of the wood toward the interior of the wood, or may decrease or increase with depth.

[0026] When the artificial opening is a non-through hole, the depth of the opening is preferably 0.1 mm or more, and more preferably 0.3 mm or more, from the viewpoint of achieving sufficient bonding strength.

[0027] The direction in which the artificial holes extend into the wood may be parallel to the grain direction, or at an angle to the grain direction, when the wood has a grain direction, such as in solid wood, LVL, or plywood. Forming the holes at an angle that is not too close to perpendicular to the grain direction may reduce the strength of the wood itself, but increases the bond strength between the wood and the resin composition. By forming the holes at an angle, the resin composition in the vessels and tracheids extending in the grain direction intersects with the resin composition in the artificial holes, bonding together at the intersections. The resin composition that penetrates into the voids becomes more entangled with the wood, which is thought to increase the bond strength.

[0028] Artificial openings can be formed, for example, by using a rotary blade, a laser, or the like on the surface of the wood. Alternatively, artificial openings can be formed by using multiple wood materials, first forming grooves in at least one of the wood materials, and then laminating the materials together so that the grooves form through holes or blind holes extending from the surface of the wood to the interior of the wood. Multiple grooves may be formed. The grooves can be formed with a rotary blade, a laser, or the like. In the case of wood made by laminating boards together, grooves may be formed in a staggered pattern on the mating surfaces of the boards that make up the materials. This is preferred because it makes it easier for artificial openings to appear when the laminated wood is cut perpendicular to the grooves.

[0029] In the case of thin or plank-shaped wood, the resin composition is bonded to the surface where there are voids so that the resin composition can penetrate in the longitudinal direction of the voids, and here, the surface where there are voids includes all surfaces surrounding the wood in the thickness direction of the wood, including the four side surfaces in the case of plywood, and the side surfaces in the case of a thin cylindrical wood. Naturally, it also includes the end grain of solid wood.

[0030] As mentioned above, sufficient joint strength is generated by the anchoring effect of the resin composition that penetrates into the voids, so there is no need to use adhesives or compatibilizers, and there is no need to apply any pretreatment to the wood joints. This eliminates the need for extra materials and simplifies the manufacturing process.

[0031] Furthermore, in the wood-resin bonded article of the present invention, the wood and resin composition are strongly bonded by the anchor effect, so even if the resin composition tries to shrink, the rigidity of the wood makes it less likely to shrink or warp. In particular, if the rigidity is high in the direction perpendicular to the joining direction, as in the case of MMP, it is easier to resist the force of resin shrinkage applied in the perpendicular direction. In addition, the pressure generated when the resin shrinks may further increase the bonding strength between the wood and resin.

[0032] [Polypropylene resin composition] The polypropylene resin composition comprises a polypropylene resin and a low molecular weight polyolefin.

[0033] <Polypropylene resin> The polypropylene resin has one or more of the following properties (1) to (3): By using a polypropylene resin composition containing such a polypropylene resin, a wood-resin joined body having sufficient joining strength can be obtained without destroying the wood. Property (1): The ethylene content is 0.8 to 10% by mass. Property (2): The crystallization onset temperature measured by differential scanning calorimetry (DSC) is 80 to 110°C. Property (3): Number average molecular weight (Mn) is more than 40,000 to 100,000.

[0034] Property (1): Ethylene content The polypropylene resin preferably has an ethylene content of 0.8 to 10% by mass, more preferably 1.6 to 8.6% by mass, and even more preferably 2.4 to 7.2% by mass. When the ethylene content of the polypropylene resin is within this range, the polypropylene resin is flexible and has high shape conformability when heated, allowing the polypropylene resin composition to effectively penetrate into voids inside the wood, resulting in a wood-resin joined body with sufficient joining strength.

[0035] The polypropylene resin may be any of propylene-ethylene random copolymer resin, propylene-ethylene block copolymer resin, and propylene-ethylene random block copolymer resin. The polypropylene resin may also be copolymerized with a small amount (for example, a content not exceeding the ethylene content) of a comonomer other than ethylene (e.g., 1-butene, 1-hexene, 1-octene, etc.).

[0036] The ethylene content of the polypropylene resin is a value measured by Fourier transform infrared spectroscopy. The contents of comonomers other than ethylene are also values ​​measured in accordance with the same method. The ethylene content of the polypropylene resin according to the present invention is measured by the CFC-IR method as follows.

[0037] (i) Analytical equipment to be used (A) Cross-sorting device Dia Instruments CFC T-100 (hereafter referred to as CFC) (a) Fourier transform infrared absorption spectroscopy FT-IR, PerkinElmer 1760X The fixed wavelength infrared spectrophotometer that was attached as a CFC detector was removed, and an FT-IR was connected instead, and this FT-IR was used as a detector. The transfer line between the outlet of the solution eluted from the CFC and the FT-IR is 1 m long and is maintained at 140°C throughout the measurement. The flow cell attached to the FT-IR has an optical path length of 1 mm and an optical path width of 5 mmφ and is maintained at 140°C throughout the measurement. (c) Gel permeation chromatography (GPC) The GPC column used in the latter stage of the CFC is three AD806MS columns manufactured by Showa Denko K.K. connected in series.

[0038] (ii) CFC measurement conditions (A) Solvent: Orthodichlorobenzene (ODCB) (a) Sample concentration: 4 mg / ml (c) Injection volume: 0.4 ml (d) Crystallization: The temperature is lowered from 140°C to 40°C over approximately 40 minutes. (E) Sorting method: The fractionation temperatures during temperature rising elution fractionation are 40°C, 100°C, and 140°C, and the mixture is fractionated into a total of three fractions. The elution proportions (unit: mass%) of the components eluting at 40°C or below (Fraction 1), the components eluting at temperatures above 40°C to 100°C (Fraction 2), and the components eluting at temperatures above 100°C to 140°C (Fraction 3) are defined as W40, W100, and W140, respectively. W40 + W100 + W140 = 100% by mass. Each separated fraction is automatically transported directly to an FT-IR analyzer. (F) Elution solvent flow rate: 1 ml / min

[0039] (iii) FT-IR measurement conditions After the sample solution starts to elute from the GPC downstream of the CFC, FT-IR measurement is carried out under the following conditions, and GPC-IR data is collected for each of the above-mentioned fractions 1 to 3. (A) Detector: Polymer char MCT (a) Resolution: 8cm -1 (c) Measurement interval: 0.2 minutes (12 seconds) (D) Number of measurements per measurement: 15

[0040] (iv) Post-processing and analysis of measurement results The elution amounts and molecular weight distributions of the components eluted at each temperature were measured using FT-IR at 2945 cm -1 The absorbance of the eluted components is calculated using a chromatogram. The elution volume is normalized so that the total elution volume of each component is 100% by mass. The retention volume is converted to molecular weight using a calibration curve prepared in advance using standard polystyrene. The standard polystyrene used is the following brand manufactured by Tosoh Corporation. F380, F288, F128, F80, F40, F20, F10, F4, F1, A5000, A2500, A1000. A calibration curve was created by injecting 0.4 ml of a solution of each compound dissolved in ODCB (containing 0.5 mg / ml of dibutylhydroxytoluene (BHT)) at 0.5 mg / ml. The calibration curve was calculated using a cubic equation obtained by approximating the curve using the least squares method.

[0041] To convert to molecular weight, a general-purpose calibration curve is used, based on "Size Exclusion Chromatography" by Sadao Mori (Kyoritsu Publishing). The viscosity formula used is ([η] = K × M α ) use the following values: (a) When creating a calibration curve using standard polystyrene PS:K = 1.38 × 10 -4 , α=0.70 (a) When measuring polypropylene resin samples PP:K = 1.03 × 10 -4 , α=0.78 The constants K and α in (a) above can be used not only for polypropylene resins in general, but also for quantifying the molecular weight and amount of the block portion of a propylene-based block copolymer. The molecular weights of the above fractionated elution fractions are defined as Mw(40), Mw(100), and Mw(140). The overall molecular weight distribution was calculated by adding up the data obtained from the three fractions. The ethylene content distribution of each eluted component (distribution of ethylene content along the molecular weight axis) was measured by FT-IR at 2956 cm-1 and absorbance at 2927cm -1 The ratio of the absorbance of polyethylene, polypropylene, 13 The ethylene content (mass%) is calculated using a calibration curve prepared in advance using ethylene propylene rubber (EPR) or a mixture of EPR whose ethylene content is known by C-NMR measurement or the like.

[0042] Characteristic (2): Crystallization start temperature The polypropylene resin preferably has a crystallization onset temperature of 80 to 110°C. The upper limit of the crystallization onset temperature is more preferably 107°C or lower, and even more preferably 104°C or lower. When the crystallization onset temperature of the polypropylene resin is within the above range, the time until the melt flow stops during heating and cooling is extended, allowing the polypropylene resin composition to effectively penetrate into voids inside the wood, resulting in a wood-resin joined body with sufficient joining strength. On the other hand, from the viewpoint of ease of molding, it is preferable that the crystallization onset temperature is not too low, and the lower limit of the crystallization onset temperature is more preferably 90°C or higher, and even more preferably 95°C or higher.

[0043] The crystallization onset temperature and crystallization temperature of a polypropylene resin are values ​​measured using a differential scanning calorimeter (DSC) in accordance with JIS-K7121. A sample is held at 200°C for 10 minutes, and then crystallized to 40°C at a cooling rate of 10°C / min. The crystallization onset temperature and crystallization temperature are determined from the DSC curve. The temperature at the intersection of the approximation line of the high-temperature side baseline of the DSC curve during crystallization and the tangent to the inflection point on the high-temperature side of the exothermic peak is taken as the crystallization onset temperature, and the maximum peak temperature of the DSC curve is taken as the crystallization temperature.

[0044] Characteristic (3): Number average molecular weight (Mn) The polypropylene resin preferably has a number average molecular weight (Mn) of more than 40,000 to 100,000, more preferably 50,000 to 90,000, and even more preferably 60,000 to 80,000. When the number average molecular weight (Mn) of the polypropylene resin is within the above range, the melt fluidity during heating is high, allowing the polypropylene resin composition to effectively penetrate into voids within the wood, resulting in a wood-resin joined body with sufficient bonding strength. The number average molecular weight (Mn) of the polypropylene resin is a value measured by gel permeation chromatography (GPC). The GPC measurement method will be described later.

[0045] The polypropylene resin has any one of the above properties (1) to (3), preferably the above properties (1) and (2), the properties (2) and (3), or the properties (3) and (1), and more preferably the above properties (1), (2), and (3).

[0046] The polypropylene resin may be used alone or in combination of two or more kinds. When the polypropylene resin is a combination of two types of polypropylene resins, examples include a combination of a polypropylene resin having one or more of the properties (1) to (3) with a polypropylene resin having one or more of the properties (1) to (3); a combination of a polypropylene resin having one or more of the properties (1) to (3) with a polypropylene resin having none of the properties (1) to (3), where the combined polypropylene resin blend has one or more of the properties (1) to (3); and a combination of two polypropylene resins having none of the properties (1) to (3), where the combined polypropylene resin blend has one or more of the properties (1) to (3). The same applies when the polypropylene resin is a combination of three or more types of polypropylene resins. Note that polypropylene resins having none of the properties (1) to (3) do not include those that fall under the category of modified polyolefins and low-molecular-weight polyolefins, which will be described later.

[0047] Characteristic (4): Crystallization temperature The polypropylene resin preferably has one or more of the above properties (1) to (3), and further has the property (4). Property (4): The crystallization temperature measured by differential scanning calorimetry (DSC) is 79 to 109°C. The crystallization temperature of the polypropylene resin is preferably 79 to 109°C, more preferably 88 to 105°C, and even more preferably 93 to 102°C. When the crystallization temperature of the polypropylene resin is within the above range, the crystallization rate is slow, and the polypropylene resin composition can sufficiently penetrate into the voids inside the wood. The method for measuring the crystallization temperature of the polypropylene resin is as described above.

[0048] When the polypropylene resin is a combination of two types of polypropylene resins, examples include a combination of two types of polypropylene resins having property (4); a combination of a polypropylene resin having property (4) and a polypropylene resin not having property (4), where the blend of the combined polypropylene resins has property (4); a combination of two types of polypropylene resins not having property (4), where the blend of the combined polypropylene resins has property (4). The same applies when the polypropylene resin is a combination of three or more types of polypropylene resins. The same applies to properties (5) to (8) described below.

[0049] Property (5): Difference between crystallization onset temperature and crystallization temperature The polypropylene resin preferably has one or more of the above properties (1) to (3), optionally has the above property (4), and further has the property (5). Property (5): The difference between the crystallization onset temperature and the crystallization temperature is 1 to 6°C. The difference between the crystallization onset temperature and the crystallization temperature of the polypropylene resin is preferably 1 to 6° C., more preferably 2 to 5° C. When the difference between the crystallization onset temperature and the crystallization temperature of the polypropylene resin is within the above range, initial crystallization can be suppressed, and the polypropylene resin composition can sufficiently penetrate into the interior of wood while maintaining its fluidity.

[0050] Characteristics (6): Mw / Mn The polypropylene resin preferably has one or more of the above properties (1) to (3), optionally has the above property (4) and / or the above property (5), and further has the property (6). Property (6): Mw / Mn is 2.0 to 4.0. (Mn is the number average molecular weight, and Mw is the weight average molecular weight.) The polypropylene resin preferably has an Mw / Mn ratio of 2.0 to 4.0, more preferably 2.0 to 3.5. Here, Mw / Mn is the ratio of weight average molecular weight (Mw) to number average molecular weight (Mn) measured by GPC. When the Mw / Mn ratio of the polypropylene resin is within the above range, swelling caused by high molecular weight components is small, and the polypropylene resin composition does not spread in the width direction, allowing it to fully penetrate into the interior of wood.

[0051] The definitions of Mn and Mw are described in "Fundamentals of Polymer Chemistry" (edited by the Society of Polymer Science, Tokyo Kagaku Dojin, 1978) and the like, and are calculated from the molecular weight distribution curve obtained by gel permeation chromatography (GPC). The GPC measurement method is as follows. Apparatus: Waters GPC (ALC / GPC 150C) Detector: FOXBORO MIRAN 1A IR detector (measurement wavelength: 3.42 μm) ·Measurement temperature: 140℃ Column: Showa Denko AD806M / S (3 columns in series) Mobile phase solvent: orthodichlorobenzene ·Flow rate: 1.0ml / min Sample preparation: Dissolve the sample in orthodichlorobenzene (containing 0.5 mg / mL of dibutylhydroxytoluene (BHT)) at 140°C for approximately 1 hour to give a sample concentration of 1 mg / mL. ·Injection amount: 0.2ml

[0052] The conversion from the retention volume obtained by GPC measurement to molecular weight is carried out using a calibration curve prepared in advance using standard polystyrene (PS). The standard polystyrenes used are all the following brands manufactured by Tosoh Corporation. F380, F288, F128, F80, F40, F20, F10, F4, F1, A5000, A2500, A1000

[0053] A calibration curve was created by dissolving each compound in orthodichlorobenzene (containing 0.5 mg / mL of BHT) at a concentration of 0.5 mg / mL and injecting 0.2 mL of the solution. The calibration curve was calculated using a cubic equation obtained by approximating the curve using the least squares method. The viscosity formula used to convert to molecular weight is [η] = K × M α The following values ​​are used: (a) When creating a calibration curve using standard polystyrene PS:K = 1.38 × 10 -4 , α=0.70 (a) When measuring polypropylene resin samples PP:K = 1.03 × 10 -4 , α=0.78 The constants K and α in (a) above can be used not only for polypropylene resins in general, but also for quantifying the molecular weight and amount of the block portion of a propylene-based block copolymer.

[0054] Property (7): Amount of components soluble in orthodichlorobenzene at 40°C The polypropylene resin preferably has one or more of the above properties (1) to (3), optionally one or more of the above properties (4) to (6), and further preferably has the property (7). Property (7): The amount of components soluble in orthodichlorobenzene at 40°C is 4.0 mass % or less. The polypropylene resin preferably has a content of components soluble in orthodichlorobenzene at 40° C. of 4.0% by mass or less, more preferably 3.0% by mass or less, and particularly preferably 1.0% by mass or less. When the content of components soluble in orthodichlorobenzene at 40° C. of the polypropylene resin is within the above range, the resulting wood-resin joined body has a good odor.

[0055] The amount of components in a polypropylene resin that are soluble in orthodichlorobenzene at 40°C is a value measured by temperature rising elution fractionation (TREF) method. The sample was dissolved in orthodichlorobenzene at 140°C to form a solution. This solution was then loaded onto a TREF column at 140°C under the following conditions. The column was then cooled to 100°C at a rate of 8°C / min, then cooled to 40°C at a rate of 4°C / min, and held there for 10 minutes. The solvent, orthodichlorobenzene, was then passed through the column at a flow rate of 1 mL / min to elute the components dissolved in orthodichlorobenzene at 40°C in the TREF column for 10 minutes. The column was then heated linearly to 140°C at a rate of 100°C / hour to obtain an elution curve. The percentage (mass%) of the amount of components eluting at 40°C relative to the total sample mass was calculated from the obtained elution curve.

[0056] The measurement conditions for TREF are as follows. Detector: FOXBORO MIRAN 1A detector (measurement wavelength: 3.42 μm) Column size: 4.3mmφ×150mm Column packing material: 100 μm surface-deactivated glass beads Solvent: orthodichlorobenzene Solvent flow rate: 1 mL / min Sample concentration: 5mg / mL Sample injection volume: 0.2 mL

[0057] Property (8): MFR (230°C, 2.16 kg load) The polypropylene resin preferably has one or more of the above properties (1) to (3), optionally one or more of the above properties (4) to (7), and further preferably has the property (8). Property (8): MFR (230°C, 2.16 kg load) is 10 to 300 g / 10 min. The polypropylene resin preferably has an MFR (230°C, 2.16 kg load) of 10 to 300 g / 10 min, more preferably 13 to 200 g / 10 min, and even more preferably 16 to 100 g / 10 min. When the MFR of the polypropylene resin is within the above range, the melt fluidity during heating is high, allowing the polypropylene resin composition to effectively penetrate into voids inside the wood, resulting in a wood-resin joined body with sufficient joining strength. The MFR of the polypropylene resin is a value measured in accordance with JIS-K7210:1982.

[0058] Polypropylene resins are propylene homopolymers obtained by homopolymerizing propylene in a single stage or two or more multistage polymerizations; propylene-α-olefin random copolymers obtained by copolymerizing propylene and an α-olefin in a single stage or two or more multistage polymerizations; polymerization step (1) in which propylene is homopolymerized in a single stage or two or more multistage polymerizations to obtain a propylene homopolymer; copolymerization step (2-1) in which propylene and an α-olefin are copolymerized in a single stage or two or more multistage polymerizations to obtain a propylene-α-olefin random copolymer; or copolymerization step (2-2) in which two or more α-olefins are copolymerized in a single stage or two or more multistage polymerizations to obtain an α-olefin random copolymer. and (2-2), a propylene-α-olefin block copolymer obtained by a polymerization comprising a copolymerization step (1) of copolymerizing propylene and an α-olefin in a single stage or two or more stages to obtain a propylene-α-olefin random copolymer, and a copolymerization step (2-1) of copolymerizing propylene and an α-olefin in a single stage or two or more stages to obtain a propylene-α-olefin random copolymer, or a copolymerization step (2-2) of copolymerizing two or more α-olefins in a single stage or two or more stages to obtain an α-olefin random copolymer. The polypropylene resin may be one type or a combination of two or more types.

[0059] The α-olefin is preferably ethylene or an α-olefin having 4 to 18 carbon atoms. Specific examples include ethylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-heptene, 4-methyl-pentene-1, 4-methyl-hexene-1, 4,4-dimethylpentene-1, etc. The α-olefin may be one type or a combination of two or more types.

[0060] The polypropylene resin is preferably one or more polypropylene resins selected from the group consisting of propylene-ethylene random copolymers, propylene-1-butene random copolymers, propylene-ethylene-1-butene random copolymers, propylene-ethylene random block copolymers, and propylene-ethylene-1-butene random block copolymers.

[0061] The polypropylene resin contains 85 to 100 mol %, preferably 90 to 99.5 mol %, and more preferably 92 to 98.5 mol % of propylene units, and 0 to 15 mol %, preferably 0.5 to 10 mol %, and more preferably 1.5 to 8 mol % of ethylene units and / or 1-butene units. Here, the propylene units and ethylene and / or 1-butene units are values ​​measured by Fourier transform infrared analysis.

[0062] Examples of polypropylene resins include those polymerized using a Ziegler-Natta catalyst, a metallocene catalyst, and a post-metallocene catalyst. Examples of Ziegler-Natta catalysts include catalysts containing a solid component essentially containing titanium, magnesium, and a halogen, an organoaluminum, and an optional electron donor. Examples of metallocene catalysts include catalysts containing a Group 4 transition metal compound containing a ligand having a cyclopentadienyl skeleton, a co-catalyst, and an optional organometallic compound and support. Examples of post-metallocene catalysts include catalysts containing an organometallic compound such as a bisamide compound of a Group 4 metal, a bisimino compound of a Group 8 to 10 metal, or a salicylaldiminato compound of a Group 4 to 10 metal, a co-catalyst, and an optional organometallic compound and support.

[0063] The polypropylene resin can be selected from commercially available products, including the WINTEC (registered trademark) series manufactured by Japan Polypropylene Corporation and the WELNEX (registered trademark) series manufactured by Japan Polypropylene Corporation.

[0064] The content of the polypropylene resin in 100% by mass of the polypropylene resin composition is preferably 10 to 99% by mass, more preferably 50 to 99 parts by mass, even more preferably 70 to 95 parts by mass, and particularly preferably 75 to 85 parts by mass. When the content of the polypropylene resin is within the above range, the polypropylene resin composition can effectively penetrate into voids inside the wood, and a wood-resin joined body with sufficient joining strength can be obtained.

[0065] <Polyolefin with a number average molecular weight (Mn) of 1,000 to 40,000> The polypropylene resin composition contains a low-molecular-weight polyolefin, which is a polyolefin having a number-average molecular weight (Mn) of 1,000 to 40,000. By using a polypropylene resin composition containing a low-molecular-weight polyolefin, it is possible to obtain a wood-resin joined body having sufficient joining strength without destroying the wood. Note that the low-molecular-weight polyolefin is not a polypropylene resin or a modified polyolefin.

[0066] Examples of polyolefins include (co)polymers of one or more olefins, and copolymers of one or more olefins with one or more other monomers. Examples of olefins include alkenes having 2 to 4 carbon atoms, such as ethylene, propylene, 1-butene, 2-butene, and isobutene; α-olefins having 5 to 30 carbon atoms (1-hexene, 1-decene, 1-dodecene, etc.); and alkenes other than α-olefins having 5 to 30 carbon atoms. Examples of other monomers include monomers having an unsaturated group having 4 to 30 carbon atoms and copolymerizable with the olefin, such as aromatic monomers such as styrene, and vinyl acetate.

[0067] Specific examples of low-molecular-weight polyolefins include ethylene unit-containing (propylene unit-free) (co)polymers such as high-density polyethylene, medium-density polyethylene, low-density polyethylene, and copolymers of ethylene and a monomer having an unsaturated group with 4 to 30 carbon atoms (e.g., butene (1-butene, etc.), α-olefins having 5 to 30 carbon atoms (1-hexene, 1-dodecene, etc.), vinyl acetate, etc.); propylene unit-containing (ethylene unit-free) (co)polymers such as polypropylene and copolymers of propylene and a monomer having an unsaturated group with 4 to 30 carbon atoms (e.g., butene (1-butene, etc.), α-olefins having 5 to 30 carbon atoms (1-hexene, 1-dodecene, etc.), vinyl acetate, etc.); ethylene / propylene copolymers; and (co)polymers of olefins having 4 or more carbon atoms, such as polybutene. Among these, ethylene homopolymers, propylene homopolymers, and ethylene / propylene copolymers are preferred, with ethylene homopolymers and propylene homopolymers being more preferred, from the viewpoint of increasing the bonding strength of wood-resin bonded structures.

[0068] The low-molecular-weight polyolefin has a number-average molecular weight (Mn) of 1,000 to 40,000, preferably 1,000 to 26,000, more preferably 1,200 to 14,000, and even more preferably 1,500 to 12,000. When the number-average molecular weight of the low-molecular-weight polyolefin is within the above range, a plasticizing effect on the polypropylene resin is exhibited without impairing the mechanical strength of a molded article of the polypropylene resin composition, thereby improving the fluidity of the polypropylene resin composition and enabling the resin to sufficiently penetrate into the interior of wood. The Mn of the low-molecular-weight polyolefin is a value measured by gel permeation chromatography (GPC), which is the same as the GPC measurement method for the polypropylene resin described above.

[0069] The softening point of the low-molecular-weight polyolefin is preferably 100 to 163° C., more preferably 105 to 150° C. When the softening point of the low-molecular-weight polyolefin is within the above range, stickiness is suppressed and operability is good, and the resin composition can sufficiently penetrate into the interior of the wood without increasing the crystallization temperature of the polypropylene resin. The softening point of the low-molecular-weight polyolefin is a value measured in accordance with JIS-K2207.

[0070] The low molecular weight polyolefin preferably has a density of 0.85 to 0.97 g / cm 3 and more preferably 0.87 to 0.92 g / cm 3 When the density of the low-molecular-weight polyolefin is within the above range, stickiness is suppressed and handling is good, the crystallization rate of the polypropylene resin can be reduced, and the resin composition can be sufficiently penetrated into the interior of the wood. The density of the low-molecular-weight polyolefin is a value measured at 20°C in accordance with JIS-K7112.

[0071] The low-molecular-weight polyolefin can be selected from commercially available products, including the Sanwax (registered trademark) series (low-molecular-weight polyethylene) manufactured by Sanyo Chemical Industries, Ltd., the Viscol (registered trademark) series (low-molecular-weight polypropylene) manufactured by Sanyo Chemical Industries, Ltd., the Hiwax (trade name) series manufactured by Mitsui Chemicals, Inc., and the Excelex (registered trademark) series manufactured by Mitsui Chemicals, Inc.

[0072] The low molecular weight polyolefins may be used alone or in combination of two or more.

[0073] The content of the low-molecular-weight polyolefin is preferably 0.1 to 100 parts by mass, more preferably 1 to 70 parts by mass, and even more preferably 5 to 40 parts by mass, relative to 100 parts by mass of the polypropylene resin. When the content of the low-molecular-weight polyolefin is within the above range, a plasticizing effect on the polypropylene resin is exhibited without impairing the mechanical strength of a molded article of the polypropylene resin composition, thereby improving the fluidity of the polypropylene resin composition. In addition, the crystallization rate of the polypropylene resin can be reduced, allowing the resin composition to sufficiently penetrate into the interior of wood.

[0074] <Modified polyolefin> From the viewpoint of further improving the bonding strength between wood and resin, it is preferable that the polypropylene resin composition further contains a modified polyolefin. The modified polyolefin refers to a resin containing polymerized units derived from an olefin monomer and polymerized units derived from a monomer having a functional group, in which the polymerized units derived from the olefin monomer account for 50 mol % or more. Examples of the functional group include a carboxyl group, a hydroxyl group, and an amino group. Note that the modified polyolefin is not the polypropylene resin or low-molecular-weight polyolefin according to the present invention. As the modified polyolefin, acid-modified polyolefin, hydroxy-modified polyolefin, etc. can be preferably used.

[0075] Examples of polyolefins include (co)polymers of one or more olefins, and copolymers of one or more olefins with one or more other monomers. Examples of olefins include alkenes having 2 to 4 carbon atoms, such as ethylene, propylene, 1-butene, 2-butene, and isobutene; α-olefins having 5 to 30 carbon atoms (1-hexene, 1-decene, 1-dodecene, etc.); and alkenes other than α-olefins having 5 to 30 carbon atoms. Examples of other monomers include monomers having an unsaturated group having 4 to 30 carbon atoms and copolymerizable with the olefin, such as aromatic monomers such as styrene, and vinyl acetate. Specific examples of polyolefins include polyethylene, polypropylene, ethylene-α-olefin copolymers, ethylene-α-olefin-non-conjugated diene compound copolymers (EPDM, etc.), and ethylene-aromatic monovinyl compound-conjugated diene compound copolymers.

[0076] Examples of the acid-modified polyolefin include random or block copolymers of an acid-modified monomer and an olefin, and copolymers obtained by graft copolymerizing the above-mentioned polyolefin with an acid-modified monomer. Examples of acid-modified monomers include unsaturated carboxylic acids and their derivatives. Examples of unsaturated carboxylic acids include compounds having a carboxyl group, such as maleic acid, fumaric acid, itaconic acid, acrylic acid, and methacrylic acid, and a polymerizable double bond into which a functional group, such as a hydroxyl group or an amino group, is optionally introduced. Examples of unsaturated carboxylic acid derivatives include acid anhydrides, esters, amides, imides, and metal salts of unsaturated carboxylic acids. Specific examples include maleic anhydride, itaconic anhydride, methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, maleic acid monoethyl ester, maleic acid diethyl ester, fumaric acid monomethyl ester, fumaric acid dimethyl ester, acrylamide, methacrylamide, maleic acid monoamide, maleic acid diamide, fumaric acid monoamide, maleimide, N-butylmaleimide, and sodium methacrylate.

[0077] The graft copolymerization is carried out, for example, by reacting the polyolefin with the acid-modified monomer in a suitable solvent using a radical generator such as benzoyl peroxide.

[0078] The content of the acid-modified monomer in the modified polyolefin is preferably 0.05 to 10% by mass, more preferably 0.1 to 5% by mass. When the content of the acid-modified monomer in the modified polyolefin is within the above range, the compatibility of the polypropylene resin composition with wood can be improved, and the adhesiveness between the resin composition that has penetrated into the wood and the wood can be improved. The content of the acid-modified monomer in the modified polyolefin is a value measured by Fourier transform infrared analysis.

[0079] The hydroxy-modified polyolefin may be a polyolefin containing a hydroxyl group-containing monomer as a constituent unit, such as allyl alcohol, 2-hydroxyethyl (meth)acrylate, or 2-hydroxypropyl (meth)acrylate.

[0080] Hydroxy-modified polyolefins can be obtained by polymerizing conjugated diene monomers by a known method such as anionic polymerization, hydrolyzing the polymer, and hydrogenating the resulting polymer. The hydroxy-modified polyolefins may have hydroxyl groups at appropriate positions, such as the terminals of the main chain or in side chains.

[0081] Examples of hydroxy-modified polyolefins include hydroxy-modified polyethylene (e.g., low-, medium-, or high-density polyethylene, linear low-density polyethylene, ultra-high molecular weight polyethylene, ethylene-(meth)acrylate copolymer, ethylene-vinyl acetate copolymer, etc.), hydroxy-modified polypropylene (e.g., polypropylene homopolymers such as isotactic polypropylene, random copolymers of propylene and α-olefins (e.g., ethylene, butene, 1-hexene, etc.), propylene-α-olefin block copolymers, etc.), and hydroxy-modified poly(4-methylpentene-1).

[0082] The content of the hydroxyl group-containing monomer in the modified polyolefin is preferably 0.1 to 20% by mass, more preferably 0.5 to 10% by mass. When the content of the hydroxyl group-containing monomer in the modified polyolefin is within the above range, the compatibility of the polypropylene resin composition with wood can be improved, and the adhesiveness between the resin composition that has penetrated into the wood and the wood can be improved. The content of the hydroxyl group-containing monomer in the modified polyolefin is a value measured by Fourier transform infrared analysis.

[0083] The modified polyolefin can be selected from commercially available products, including the UMEX (registered trademark) series manufactured by Sanyo Chemical Industries, Ltd., the ADTEX (registered trademark) series manufactured by Japan Polyethylene Corporation, the MODIC (registered trademark) series manufactured by Mitsubishi Chemical Corporation, the ADMER (registered trademark) series manufactured by Mitsui Chemicals, Inc., and the AUROUREN (registered trademark) series manufactured by Nippon Paper Industries Co., Ltd.

[0084] The modified polyolefin may be used alone or in combination of two or more. From the viewpoint of compatibility with polypropylene resin, the modified polyolefin is preferably maleic acid-modified polypropylene or maleic acid-modified polyethylene, and more preferably maleic acid-modified polypropylene.

[0085] The content of the modified polyolefin is preferably 0.1 to 20 parts by mass, more preferably 0.5 to 10 parts by mass, and even more preferably 1 to 5 parts by mass, relative to 100 parts by mass of the polypropylene resin. When the content of the modified polyolefin is within the above range, the compatibility of the polypropylene resin composition with wood can be improved, and the adhesiveness between the resin composition that has penetrated into the wood and the wood can be improved.

[0086] <Filler> The polypropylene resin composition may further contain a filler. Use of a polypropylene resin composition containing a filler makes it easier to obtain a wood-resin joined article with less warping. The filler includes inorganic fillers, organic fillers, etc.

[0087] Examples of inorganic fillers include inorganic oxides such as silica, diatomaceous earth, barium ferrite, beryllium oxide, pumice, and pumice balloons; inorganic hydroxides such as aluminum hydroxide, magnesium hydroxide, and basic magnesium carbonate; carbonates such as calcium carbonate, magnesium carbonate, dolomite, and dawsonite; sulfates or sulfites such as calcium sulfate, barium sulfate, ammonium sulfate, and calcium sulfite; silicates such as talc, clay, mica, glass fiber, glass balloons, glass beads, calcium silicate, wollastonite, montmorillonite, and bentonite; carbons such as carbon black, graphite, carbon fiber, and hollow carbon spheres; molybdenum sulfide, boron fiber, zinc borate, barium metaborate, calcium borate, sodium borate, magnesium oxysulfate, basic magnesium sulfate fiber, potassium titanate fiber, aluminum borate fiber, calcium silicate fiber, calcium carbonate fiber, and various metal fibers.

[0088] Examples of organic fillers include husk fibers such as rice husks, wood flour, cotton, jute, paper strips, cellophane strips, aromatic polyamide fibers, cellulose fibers, nylon fibers, polyester fibers, polypropylene fibers, and thermosetting resin powders.

[0089] Among these, from the viewpoint of improving the rigidity of the polypropylene resin composition and suppressing warping of the resulting wood-resin bonded body, the filler is preferably talc or glass fiber, and particularly preferably glass fiber.

[0090] The filler may be surface-treated with an organic titanate coupling agent, an organic silane coupling agent, a fatty acid, a fatty acid metal salt, a fatty acid ester, or a modified polyolefin grafted with an unsaturated carboxylic acid or an anhydride thereof.

[0091] There is no limitation on the shape of the filler, and any shape such as granular, plate-like, rod-like, fibrous, whisker-like, etc. can be used.

[0092] The filler can be selected from commercially available products.

[0093] The fillers may be used alone or in combination of two or more. From the viewpoint of improving the rigidity of the polypropylene resin composition and suppressing warpage of the resulting wood-resin bonded body, preferred are flake-like fillers having an average particle size of 1 μm to 150 μm, particularly flake-like fillers having an average particle size of 1.5 μm to 15 μm (e.g., talc); and fibrous or whisker-like fillers having an average fiber diameter of 40 μm or less, particularly fibrous or whisker-like fillers having an average fiber diameter of 30 μm or less (e.g., basic magnesium sulfate fiber and glass fiber). Among these, talc having an average particle size of 2 μm to 8 μm and glass fiber having an average fiber diameter of 3 to 25 μm and an average fiber length of 1 to 20 mm are more preferred, and glass fiber having an average fiber diameter of 6 to 15 μm and an average fiber length of 2 to 10 mm are particularly preferred. The average particle size of the filler is a value measured using a laser diffraction / scattering particle size distribution analyzer. An example of the measuring device is the LA-920 model manufactured by Horiba, Ltd. The average fiber diameter and average fiber length are values ​​measured using a microscope or the like.

[0094] The content of the filler is preferably 5 to 30 parts by mass, more preferably 10 to 25 parts by mass, and even more preferably 10 to 20 parts by mass, relative to 100 parts by mass of the polypropylene resin. When the content of the filler is within the above range, warping of the wood-resin joined body can be reduced without impairing the bond between the wood and the polypropylene resin composition.

[0095] <Other ingredients> The polypropylene resin composition may further contain optional components other than the polypropylene resin, low-molecular-weight polyolefin, modified polyolefin, and filler. Examples of such optional components include nucleating agents, heat stabilizers, antioxidants, weathering stabilizers, light stabilizers, UV absorbers, antistatic agents, slip agents, antiblocking agents, anti-fogging agents, neutralizing agents, metal deactivators, surfactants, compatibilizers, colorants, antibacterial and antifungal agents, flame retardants, plasticizers, dispersants, conductive agents, preservatives, fragrances, deodorizers, and insect repellents; and resins such as elastomers other than polypropylene resin, low-molecular-weight polyolefin, and modified polyolefin. Two or more of these optional components may be used in combination. Furthermore, these optional components may be blended with the polypropylene resin, low-molecular-weight polyolefin, modified polyolefin, and filler, and two or more of each of the above optional components may be used in combination.

[0096] [Method of producing polypropylene resin composition] The polypropylene resin composition can be produced by mixing a polypropylene resin and a low-molecular-weight polyolefin, as well as an optional modified polyolefin, a filler, and other components, or by heating and kneading them using a single-screw extruder, a twin-screw extruder, etc. The resin temperature during heating and kneading is in the range of 100°C to 300°C and can be appropriately determined taking into account the load on the kneading, etc.

[0097] [Wood-resin bonded body and its manufacturing method] In the wood-resin bonded article, the polypropylene resin composition penetrates into voids on the surface of the wood that originate from vessels, tracheids or artificial openings, thereby bonding the wood and the resin composition together. The extent to which the polypropylene resin composition has penetrated into the voids on the wood surface can be confirmed using X-ray CT. X-ray CT involves irradiating the target sample with X-rays from all directions (360 degrees) and detecting the transmitted radiation to determine the material and internal structure of the target sample. X-rays, electromagnetic waves with wavelengths between 1 pm and 10 nm, penetrate a material and are absorbed by various factors before passing through. CT (scanning device) utilizes the differences in the "penetration rate" and "absorption rate" of the aforementioned X-rays as they pass through the target sample to examine the material and structure of the sample's interior, thereby determining the extent to which the polypropylene resin composition has penetrated into the voids on the wood surface. X-ray CT can be used not only for materials composed of different materials, but also for measuring the difference in the X-ray absorption coefficient of the same material due to differences in density.

[0098] The wood-resin bonded body can be produced as follows. A wood-resin joined body can be produced by placing wood in a mold cavity, clamping the mold, injecting a plasticized polypropylene resin composition into the mold, and solidifying it to integrate the wood and a molded product of the resin composition.

[0099] The mold only needs to be set at the joint and the resin composition portion, and does not necessarily need to be set over the entire part, including the wood portion. When the mold is not set over the entire part, the wood and the mold only need to be in close contact where the mold is set, and naturally, they will not be in close contact where the mold is not set. Therefore, compared to molding a resin composition alone, the resin volume or resin area of ​​the mold is smaller, so the mold and injection molding machine capacity can be reduced, and even if the wood portion is curved, there is no need to prepare a mold that fits that part. Miniaturizing the mold leads to easier handling and reduced costs, and is particularly useful when manufacturing large objects such as car bodies.

[0100] From the viewpoint of reducing scorching of the wood, the temperature of the resin composition during injection molding is preferably 160° C. to 200° C. The injection pressure during injection molding is preferably 10 to 25 MPa from the viewpoint of applying pressure to the wood that does not split the wood.

[0101] Wood-resin bonded products can be used as materials for, for example, interior and exterior components of automobiles, mobile phone cases, housings for personal computers and home appliances, returnable cups, furniture, toys, and the like. [Example]

[0102] The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

[0103] [Evaluation of polypropylene resin] 1. Ethylene content The ethylene content of the polypropylene resin was measured by the CFC-IR method as follows.

[0104] (i) Analytical equipment to be used (A) Cross-sorting device Dia Instruments CFC T-100 (hereafter referred to as CFC) (a) Fourier transform infrared absorption spectroscopy FT-IR, PerkinElmer 1760X The fixed wavelength infrared spectrophotometer that was attached as a CFC detector was removed and replaced with an FT-IR, which was then used as the detector. The transfer line between the outlet of the solution eluted from the CFC and the FT-IR was 1 m long and maintained at 140°C throughout the measurement. The flow cell attached to the FT-IR had an optical path length of 1 mm and an optical path width of 5 mmφ and was maintained at 140°C throughout the measurement. (c) Gel permeation chromatography (GPC) The GPC column used in the post-CFC stage was three AD806MS columns manufactured by Showa Denko K.K. connected in series.

[0105] (ii) CFC measurement conditions (A) Solvent: Orthodichlorobenzene (ODCB) (a) Sample concentration: 4 mg / ml (c) Injection volume: 0.4 ml (d) Crystallization: The temperature was lowered from 140°C to 40°C over approximately 40 minutes. (E) Sorting method: The fractionation temperatures during temperature rising elution fractionation were 40°C, 100°C, and 140°C, and the mixture was fractionated into a total of three fractions. The elution proportions (unit: mass%) of the components eluting at 40°C or below (Fraction 1), the components eluting at temperatures above 40°C to 100°C (Fraction 2), and the components eluting at temperatures above 100°C to 140°C (Fraction 3) were defined as W40, W100, and W140, respectively. W40 + W100 + W140 = 100% by mass. Each separated fraction was automatically transported directly to an FT-IR analyzer. (F) Elution solvent flow rate: 1 ml / min

[0106] (iii) FT-IR measurement conditions After the sample solution started to elute from the GPC downstream of the CFC, FT-IR measurement was carried out under the following conditions, and GPC-IR data was collected for each of the above-mentioned fractions 1 to 3. (A) Detector: Polymer char MCT (a) Resolution: 8cm -1 (c) Measurement interval: 0.2 minutes (12 seconds) (D) Number of measurements per measurement: 15

[0107] (iv) Post-processing and analysis of measurement results The elution amounts and molecular weight distributions of the components eluted at each temperature were measured using FT-IR at 2945 cm -1 The absorbance of each component was calculated using a chromatogram. The elution volume was normalized so that the total elution volume of each component was 100% by mass. The retention volume was converted to molecular weight using a calibration curve prepared in advance using standard polystyrene. The standard polystyrene used is the following brand manufactured by Tosoh Corporation. F380, F288, F128, F80, F40, F20, F10, F4, F1, A5000, A2500, A1000. A calibration curve was created by injecting 0.4 ml of a solution of each compound dissolved in ODCB (containing 0.5 mg / ml of dibutylhydroxytoluene (BHT)) at a concentration of 0.5 mg / ml. The calibration curve was a cubic equation obtained by approximating the curve using the least squares method.

[0108] For conversion to molecular weight, a general calibration curve was used based on "Size Exclusion Chromatography" by Sadao Mori (Kyoritsu Publishing). The viscosity formula used in this case ([η] = K × M α ) the following values ​​were used: (a) When creating a calibration curve using standard polystyrene PS:K = 1.38 × 10 -4 , α=0.70 (a) When measuring polypropylene resin samples PP:K = 1.03 × 10 -4 , α=0.78 The molecular weights of the fractions were defined as Mw(40), Mw(100), and Mw(140). The overall molecular weight distribution was calculated by adding up the data obtained from the three fractions. The ethylene content distribution of each eluted component (distribution of ethylene content along the molecular weight axis) was measured by FT-IR at 2956 cm -1 and absorbance at 2927cm -1 The ratio of the absorbance of polyethylene, polypropylene, 13 The ethylene content (mass%) was calculated using a calibration curve prepared in advance using ethylene-propylene-rubber (EPR) and its mixtures, whose ethylene content was known by C-NMR measurement or other methods.

[0109] 2. Differential Scanning Calorimetry (DSC) The crystallization onset temperature and crystallization temperature of polypropylene resin were measured using a differential scanning calorimeter (DSC) in accordance with JIS-K7121. A sample was held at 200°C for 10 minutes, and then crystallized to 40°C at a cooling rate of 10°C / min, to obtain a DSC curve. The temperature at the intersection of the approximate line of the high-temperature side baseline of the obtained DSC curve and the tangent to the inflection point on the high-temperature side of the exothermic peak was defined as the crystallization onset temperature, and the maximum peak temperature of the DSC curve was defined as the crystallization temperature.

[0110] 3. Number average molecular weight and weight average molecular weight The number average molecular weight and weight average molecular weight of the polypropylene resin were calculated from a molecular weight distribution curve obtained by gel permeation chromatography (GPC). The GPC measurement method was as follows. Apparatus: Waters GPC (ALC / GPC 150C) Detector: FOXBORO MIRAN 1A IR detector (measurement wavelength: 3.42 μm) ·Measurement temperature: 140℃ Column: Showa Denko AD806M / S (3 columns in series) Mobile phase solvent: orthodichlorobenzene ·Flow rate: 1.0ml / min Sample preparation: The sample was dissolved in orthodichlorobenzene (containing 0.5 mg / mL of dibutylhydroxytoluene (BHT)) at 140°C for approximately 1 hour so that the sample concentration was 1 mg / mL. ·Injection amount: 0.2ml

[0111] The conversion from the retention volume obtained by GPC measurement to molecular weight was carried out using a calibration curve prepared in advance using standard polystyrene (PS). The standard polystyrenes used were all the following brands manufactured by Tosoh Corporation. F380, F288, F128, F80, F40, F20, F10, F4, F1, A5000, A2500, A1000

[0112] A 0.2 mL solution of each compound dissolved in orthodichlorobenzene (containing 0.5 mg / mL BHT) was injected to prepare a calibration curve, which was fitted using a cubic equation obtained by the least squares method. The viscosity formula used to convert to molecular weight is [η] = K × M α The following values ​​were used: (a) When creating a calibration curve using standard polystyrene PS:K = 1.38 × 10 -4 , α=0.70 (a) When measuring polypropylene resin samples PP:K = 1.03 × 10 -4 , α=0.78

[0113] 4. The amount of components soluble in orthodichlorobenzene at 40°C The amount of components soluble in o-dichlorobenzene at 40°C in polypropylene resin was measured by temperature rising elution fractionation (TREF). The sample was dissolved in orthodichlorobenzene at 140°C to form a solution. This solution was introduced into a TREF column at 140°C under the following conditions, then cooled to 100°C at a rate of 8°C / min, then cooled to 40°C at a rate of 4°C / min, and held there for 10 minutes. The solvent, orthodichlorobenzene, was then passed through the column at a flow rate of 1 mL / min to elute the components dissolved in orthodichlorobenzene at 40°C in the TREF column for 10 minutes. The column was then heated linearly to 140°C at a rate of 100°C / hour, and an elution curve was obtained. The ratio (mass%) of the amount of components eluting at 40°C to the total amount of sample was calculated from the obtained elution curve.

[0114] The measurement conditions for TREF are as follows. Detector: FOXBORO MIRAN 1A detector (measurement wavelength: 3.42 μm) Column size: 4.3mmφ×150mm Column packing material: 100 μm surface-deactivated glass beads Solvent: orthodichlorobenzene Solvent flow rate: 1 mL / min Sample concentration: 5mg / mL Sample injection volume: 0.2 mL

[0115] 5. MFR (Temperature 230℃, Load 2.16kg) The MFR of the polypropylene resin was measured in accordance with JIS-K7210:1982.

[0116] [Raw materials used] <Polypropylene resin> The following polypropylene resin was used. The physical properties of the polypropylene resin are shown in Table 1. Polypropylene resin A (WINTEC (registered trademark) WSX03 manufactured by Japan Polypropylene Corporation, propylene-based random copolymer, MFR (temperature 230°C, load 2.16 kg) = 25 g / 10 min, Mw / Mn = 2.4) Polypropylene resin B (WELNEX (registered trademark) RMG02 manufactured by Japan Polypropylene Corporation, propylene-based block copolymer, MFR (temperature 230°C, load 2.16 kg) = 20 g / 10 min, Mw / Mn = 2.5)

[0117] [Table 1]

[0118] <Low molecular weight polyolefin> The following materials were used as low molecular weight polyolefins. Low molecular weight polypropylene: Viscol (registered trademark) 660-P manufactured by Sanyo Chemical Industries, Ltd.: number average molecular weight 8,000 Low molecular weight polyethylene: Sanwax (registered trademark) 171-P manufactured by Sanyo Chemical Industries, Ltd.: number average molecular weight 9,500

[0119] <Modified polyolefin> The following materials were used as modified polyolefins. Maleic acid-modified polypropylene: Modic (registered trademark) P928 manufactured by Mitsubishi Chemical Corporation: Modification rate 1.82% by mass

[0120] Example 1 Production of polypropylene resin composition Each component of the polypropylene resin composition shown in Table 2 was weighed and mixed uniformly using a ribbon blender. The resulting mixture was fed into a twin-screw extruder with a screw diameter of 15 mm, kneaded at a resin temperature of 200°C, extruded into strands, cooled with water, and pelletized to obtain a polypropylene resin composition.

[0121] Manufacturing of thin wood resin joints The thin wooden boards used were thin-layered multi-layer wood products (Micro Multiple Plywood, hereafter referred to as MMP) derived from cedar wood. This MMP was made by stacking nine layers of 0.15 mm thick cedar veneers with the fiber direction perpendicular to each other (9 ply, 1.5 mm thick). This MMP was made by cutting the cedar veneers with a laser and applying a phenolic resin adhesive at 10 g / m per adhesive layer. 2 Manufactured using. An MMP was placed in a mold for a plate-shaped molded product so that its front and back surfaces were in close contact with the mold. Pellets of a polypropylene resin composition were loaded into an injection molding machine, and the resin composition was injected from the injection molding machine into the mold via a spool, runner, and gate. Injection pressure was applied to one side of the thin wooden plate to form an MMP resin joint as shown in Figure 1. In Figure 1, the polypropylene resin composition part was in the shape of a plate measuring 100 mm (joint part) x 150 mm x 1.5 mm (thickness). The molding conditions were as follows: Injection pressure: 20 MPa, resin temperature: 180°C, mold temperature: 40°C

[0122] Example 2 An MMP resin conjugate of Example 2 was produced in the same manner as in Example 1, except that the polypropylene resin composition in Example 1 was changed to one shown in Table 2.

[0123] Reference Examples 1 and 2 MMP resin conjugates of Reference Examples 1 and 2 were prepared in the same manner as in Example 1, except that the polypropylene resin compositions in Example 1 were changed to those shown in Table 2.

[0124] [Evaluation of wood-resin joints] For the MMP resin bonded bodies obtained in Examples 1 and 2 and Comparative Examples 1 and 2, the state of the bonding surface between the wood and the resin was evaluated as follows.

[0125] <Wood fracture state> The splitting fracture state of the wood due to the injection pressure was evaluated according to the following criteria. The results are shown in Table 2. ◎: No resin intrusion was observed in the wood laminate, and there was no change in appearance. ○: Resin intrusion was observed in the wood laminate, but there was no change in appearance. ×: Resin invaded the wood laminate and peeled off significantly.

[0126] <Bonding state> For those with a wood fracture state other than ×, the bonding surface between the wood and the resin was evaluated according to the following criteria. The results are shown in Table 2. ○: It does not come off even when the bonding surface is pulled. ×: It is not bonded and comes off easily when touched.

[0127]

Table 2

[0128] For the wood-resin bonded bodies of Examples 1 and 2 using the polypropylene resin composition blended with the low molecular weight polyolefin, no resin intrusion was observed in the wood laminate, and the wood fracture state was superior compared to the wood-resin bonded bodies of Comparative Examples 1 and 2 without the low molecular weight polyolefin blend.

[0129] <Observation of bonding state by X-ray CT> The wood-resin bonded structure of Example 1 was observed using X-ray CT to examine the state of resin penetration into the wood pores. Measurements were performed using a MicroCT-50 manufactured by SCANCO MEDICAL. A sample of the bonded portion of the wood-resin bonded structure was cut to approximately 9 mm diameter and placed in a dedicated measurement folder. X-ray scanning was performed over 3.4 hours using an X-ray tube output of 45 kV and 88 μA (4 W), obtaining 3D image data with a resolution of 3 μm per voxel. The resulting 3D image is shown in Figure 2. Pores in the wood without resin penetration appear black, while pores in the wood with resin penetration appear gray. As shown in Figure 2, resin penetration into the wood pores was clearly confirmed in the wood-resin bonded structure of Example 1. [Industrial Applicability]

[0130] The polypropylene resin composition of the present invention can be suitably used for joining to wood having voids on the surface thereof derived from vessels, tracheids, or artificial openings. The wood-resin joined article of the present invention can be suitably used as a material for, for example, automobile interior / exterior components, mobile phone cases, housings for personal computers and home appliances, returnable cups, furniture, toys, etc. [Explanation of symbols]

[0131] 1 Polypropylene resin composition 2 Thin wood 3. Joint position (boundary between polypropylene resin composition and wood)

Claims

1. A polypropylene resin composition for bonding to a wood surface having voids derived from vessels, tracheids or artificial openings in thin or plank-shaped wood, the polypropylene resin composition comprising a polypropylene resin and a polyolefin having a number average molecular weight (Mn) of 1,500 to 12,000, provided that the polyolefin is not the polypropylene resin or a modified polyolefin, The polypropylene resin composition has the following property (1) and one or more of the following properties (2) or (3): Property (1): The ethylene content is 0.8 to 10% by mass. Property (2): The crystallization onset temperature measured by differential scanning calorimetry (DSC) is 80 to 110°C. Property (3): Number average molecular weight (Mn) is more than 40,000 to 100,000.

2. The polypropylene resin composition according to claim 1, wherein the polypropylene resin has the following property (4): Property (4): Crystallization temperature measured by differential scanning calorimetry (DSC) is 79 to 109°C.

3. The polypropylene resin composition according to claim 1 or 2, wherein the polypropylene resin has the following property (5): Property (5): The difference between the crystallization onset temperature and the crystallization temperature is 1 to 6°C.

4. The polypropylene resin composition according to any one of claims 1 to 3, wherein the polypropylene resin has the following property (6): Property (6): Mw / Mn is 2.0 to 4.

0. (Mn is the number average molecular weight, and Mw is the weight average molecular weight.)

5. The polypropylene resin composition according to any one of claims 1 to 4, further comprising a modified polyolefin.

6. The polypropylene resin composition according to any one of claims 1 to 5, further comprising a filler.

7. A wood-resin joined article comprising wood and the polypropylene resin composition according to any one of claims 1 to 6, wherein the polypropylene resin composition penetrates into the voids on the surface of the wood.

8. 8. A method for producing a wood-resin joined product according to claim 7, comprising the steps of placing a piece of wood in a mold cavity and injecting a plasticized resin composition into the mold.

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