Mold sealing material, mold set, method for producing mold sealing material, and urethane resin

Abstract

The main purpose of the technology according to the present invention is to provide a mold sealing material that, when used as a sealing material on joint surfaces of two or more molds of a mold set to mold a resin in a cavity formed by mating said molds, can improve the adhesion between the joint surfaces of the molds.　As a result of intensive studies, the present inventors have discovered that adhesion of joint surfaces of molds can be improved by installing a mold sealing material containing a urethane resin and having a specific reference axis, in one of three mutually orthogonal axial directions, having an expansion coefficient greater than the expansion coefficients accompanying a temperature change in the other two axial directions by a certain amount or more, so that the specific reference axis direction coincides with a normal direction to the joint surfaces of the molds.

Description

Sealing material for mold, mold set, method for manufacturing sealing material for mold, and urethane resin

[0001] This technology relates to a sealing material for a mold, a mold set, a method for manufacturing a sealing material for a mold, and a urethane resin.

[0002] Conventionally, a technique for molding a resin using a mold has been known.

[0003] For example, in Patent Document 1 below, a technique is disclosed in which a urethane raw material is sprayed on a sealing portion of a foam molding die to form a urethane foam that functions as a sealing material and also serves as a part of a molded product on the sealing portion.

[0004] Japanese Patent Laid-Open No. 1-196315

[0005] The main object of this technology is to provide a sealing material for a mold that can improve the adhesion of the joint surface between molds when used as a sealing material on the joint surface between molds of a mold set for molding a resin in a cavity formed by fitting two or more molds together.

[0006] As a result of intensive research, the inventors have found that a sealing material for a mold containing a urethane resin and having a specific reference axis with an expansion rate greater than or equal to a certain level compared to the expansion rates in the other two mutually orthogonal axial directions in the three axial directions can improve the adhesion of the joint surface between molds by installing it such that the specific reference axis direction coincides with the normal direction to the joint surface between molds.

[0007] That is, in this technology, a sealing material for a mold is provided that contains a urethane resin and has a reference axis with an expansion rate represented by the following formula (1) of 0.60% or more and twice or more the expansion rate in the other two axial directions. The Asker D hardness (23°C) of the mold sealing material of this technology may be 30 or higher. Next, this technology provides a mold set for molding resin in a cavity formed by joining two or more molds, wherein a groove is formed on at least one of the joining surfaces of the two or more molds, and the mold sealing material of this technology is installed such that a straight line perpendicular to the groove from the joining surface coincides with the reference axis. Furthermore, this technology provides a method for manufacturing the mold sealing material, comprising the steps of: injecting a liquid urethane raw material composition into a groove formed on at least one of the joining surfaces of the two or more molds; and curing the joint surface with the groove formed on it by joining it with the other joint surfaces, thereby trapping the urethane raw material composition within the groove. In addition, this technology provides a urethane resin having a reference axis in which, among three mutually orthogonal axial directions, the expansion rate shown by the following formula (1) is 0.60% or higher, and is at least twice the expansion rate in the other two axial directions.

[0008] This is an illustrative diagram of the mold sealing material of this technology. This is a perspective view of an example of a mold set provided with a sealing layer formed by the mold sealing material of this technology. This is a cross-sectional view of an example of a mold set in which the mold sealing material of this technology is installed. This is an enlarged view of the vicinity of the mold sealing material in a mold set in which the mold sealing material of this technology is installed. This is an enlarged view of the vicinity of the mold sealing material in a modified example of a mold set in which the mold sealing material of this technology is installed.

[0009] The following describes preferred embodiments for implementing this technology. The embodiments described below are examples of typical embodiments of this technology, and any combination of these embodiments is possible. Furthermore, this does not mean that the scope of this technology will be narrowed.

[0010] [Sealing material for molds] The sealing material for molds in this technology is used to form a sealing layer provided on at least one of the joining surfaces of two or more molds in a mold set described later.

[0011] The mold sealing material of this technology contains urethane resin and has a specific reference axis whose expansion rate is a certain amount greater than the expansion rate in the other two axes (out of three mutually orthogonal axes) due to temperature changes. In other words, when heated, the mold sealing material of this technology expands specifically in a specific direction (the direction of the reference axis). Also, when cooled, the mold sealing material of this technology contracts specifically in a specific direction (the direction of the reference axis). Generally, when molding resin using a mold set, the mold set is heated. Therefore, by installing the mold sealing material of this technology so that its reference axis direction coincides with the direction normal to the joint surface between the molds, the mold sealing material of this technology expands significantly (specifically) in the reference axis direction during resin molding (heating), thereby improving the adhesion (sealing performance) of the joint surface between the molds.

[0012] Here, the expansion rate associated with the temperature change refers to the expansion rate shown in the following formula (1), and hereafter, in this specification, "expansion rate" refers to the expansion rate shown in the following formula (1).

[0013]

[0014] Furthermore, in the mold sealing material of this technology, the expansion rate of the reference axis is greater than or equal to a certain amount than the expansion rate of the other two axes among the three mutually orthogonal axes, so that the mold sealing material of this technology can expand significantly in the direction of the reference axis when heated during resin molding, etc. In the mold sealing material of this technology, the expansion rate of the reference axis is preferably twice or more than the expansion rate in the other two axes, and more preferably 2.5 times or more.

[0015] There is no particular upper limit to the expansion rate of the reference axis relative to the expansion rates in the other two axes, but it can be adjusted to, for example, 50 times or less, 30 times or less, 20 times or less, or the expansion rates in the other two axes.

[0016] Here, the expansion rates in the two axes being compared for the expansion rate of the reference axis may or may not be the same.

[0017] In the mold sealing material of this technology, first, an axis exhibiting a significantly larger expansion rate than the expansion rates in other directions is identified as the reference axis. This allows two axes mutually orthogonal to the reference axis to be identified as the other two axis directions.

[0018] Let's explain this in more detail using the conceptual diagram of the mold seal material shown in Figure 1. Figure 1(a) shows the mold seal material under room temperature conditions (23°C), and Figure 1(b) shows the mold seal material under heated conditions (60°C). By comparing Figure 1(a) and Figure 1(b), it can be confirmed that the mold seal material under heated conditions (60°C) expands significantly in the Y-axis direction compared to the mold seal material under room temperature conditions (23°C). On the other hand, it can be confirmed that the shape does not expand significantly in directions other than the Y-axis. In other words, in the mold seal material shown in Figure 1, there is a Y-axis that shows a significantly larger expansion rate than the expansion rates in other directions. In the mold seal material, by identifying the Y-axis as the reference axis, the X-axis and Z-axis, which are mutually orthogonal to the Y-axis (reference axis), can be identified as the other two axis directions, as shown in Figure 1.

[0019] Furthermore, since the mold sealing material of this technology can control the direction of expansion in response to heating in the direction of the reference axis, in a mold set in which grooves are formed on the joining surfaces of molds, by positioning the mold sealing material so that its reference axis coincides with a straight line perpendicular to the direction from the joining surface to the deepest part of the groove, the load generated by expansion on the joining surface between the mold sealing material and the groove during heating such as molding can be reduced.

[0020] As specified above, the expansion rate of the reference axis of the mold sealing material of this technology is adjusted to, for example, 0.60% or more, 0.80% or more, 1.00% or more, and 1.20% or more. When the mold sealing material is installed so that the reference axis direction coincides with the direction normal to the joint surface between the molds, the adhesion between the joint surfaces of the molds can be effectively improved during resin molding (heating).

[0021] There is no particular upper limit to the expansion rate of the reference axis of the mold sealing material of this technology. For example, it may be prepared with an expansion rate of 15.0% or less, 10.0% or less, or 5.0% or less.

[0022] The mold sealing material of this technology consists of a cured product of a urethane raw material composition. The urethane raw material composition mainly contains a urethane resin raw material (a mixture containing at least a polyol component and a polyisocyanate component). For example, if the mold sealing material of this technology consists only of urethane resin, the urethane raw material composition consists only of urethane resin raw material. The urethane raw material composition can be prepared, for example, by mixing and stirring a first liquid containing at least a polyol component and a second liquid containing at least a polyisocyanate component.

[0023] The mold sealing material of this technology contains urethane resin, but this urethane resin is not a foam. In other words, the urethane resin used in the mold sealing material is not what is commonly known as urethane foam. Furthermore, the mold sealing material of this technology is not formed with the intention of becoming part of a molded product. In this technology, "not a foam" means that foaming is not intentionally induced. For example, if a small portion of the resin naturally foams due to moisture in the air when forming a sealing layer using the mold sealing material of this technology, this is not intentional foaming and is therefore included in the concept of "not a foam."

[0024] Furthermore, the "urethane resin" contained in the mold sealing material of this technology is a polymer compound having urethane bonds formed by the reaction of a polyol component and a polyisocyanate component. As long as the purpose of this technology is not impaired, any combination of polyol component and polyisocyanate component can be used to synthesize the urethane resin that can be used in the mold sealing material of this technology under any conditions. For example, a urethane resin having a polyester structure is preferred as the urethane resin that can be used in the mold sealing material of this technology.

[0025] The polyester structure is not particularly limited as long as it does not impair the purpose of this technology, but for example, a polycaprolactone structure derived from a caprolactone structure and produced by ring-opening the caprolactone structure is preferred. More specifically in this case, a urethane resin synthesized under arbitrary conditions by combining a polyester polyol component and an arbitrary polyisocyanate component, or more preferably a urethane resin synthesized under arbitrary conditions by combining an arbitrary polycaprolactone polyol component produced by ring-opening polymerization using a caprolactone monomer and an arbitrary polyisocyanate component, may be used as the urethane resin for the mold sealing material of this technology. By using the above resin, a urethane resin having a reference axis whose expansion rate is a certain amount greater than the expansion rates in the other two axes among the three mutually orthogonal axes can be suitably prepared. Furthermore, physical properties such as Aska-D hardness (23°C) and elongation (60°C), which will be described later, can be efficiently prepared within a suitable range.

[0026] Furthermore, it is presumed that the urethane resin used in this technology contains a structure that changes state with temperature, causing it to expand specifically in one direction (corresponding to the reference axis) when heated and to contract back to its original size when cooled. For example, polycaprolactone is generally known as a crystalline substance, and its melting point is approximately 60°C. Therefore, it is presumed that the urethane resin used in this technology contains a structure such as this polycaprolactone structure, causing the polycaprolactone structure in the urethane resin to change from a crystalline state to an amorphous state when heated (for example, when heating a mold). It is also presumed that when the heated urethane resin cools, the polycaprolactone structure returns from the amorphous state back to a crystalline state.

[0027] The mold sealing material of this technology may contain other components such as resins other than urethane resin, fillers, catalysts, thickeners, and solvents, as necessary, as long as it does not impair the purpose of this technology. The percentage of urethane resin in the total amount (100% by mass) of the mold sealing material is not particularly limited as long as it does not impair the purpose of this technology, but for example, 85% by mass or more is preferred, 90% by mass or more is more preferred, and 95% by mass or more is even more preferred. The upper limit for the percentage of urethane resin in the total amount (100% by mass) of the mold sealing material may be 100% by mass.

[0028] [Example of a method for manufacturing mold sealing material] The method for manufacturing the mold sealing material of this technology is not particularly limited. For example, the mold sealing material of this technology can be suitably manufactured by performing the steps of: injecting a liquid urethane raw material composition into a groove formed in at least one of the joining surfaces of two or more molds; and joining the joining surface in which the groove is formed with the other joining surfaces and curing the urethane raw material composition while it is trapped in the groove.

[0029] In this case, the other mold is fitted into the mold having a groove formed on its joint surface, and the joint surface with the groove is brought together with the other joint surface to form a mold seal molding cavity that defines the shape of the mold seal material of this technology.

[0030] In this mold, the axial direction corresponding to the straight line perpendicular to the joint surface between the molds and the deepest part of the groove is sealed by the joining of the molds. In contrast, the other two axial directions, which are mutually perpendicular to this axial direction, are always sealed by the molds.

[0031] Furthermore, the aforementioned "liquid urethane raw material composition" is, as previously stated, a liquid mixture containing at least a polyol component and a polyisocyanate component. In this specification, "liquid" includes a state having a predetermined viscosity and fluidity (for example, syrup-like).

[0032] Using the above-described mold, the liquid urethane raw material composition is injected into a groove formed in at least one of the joining surfaces of two or more molds, and the joining surface with the groove is brought together with the other joining surfaces to confine the urethane raw material composition within the groove. As a result, urethane resin is synthesized from the liquid urethane raw material composition within the mold sealing material molding cavity (with the urethane raw material composition confined within the groove). This allows for the suitable manufacture of the mold sealing material of this technology.

[0033] Furthermore, in the mold sealing material manufactured by the above manufacturing method, the expansion rate in the axial direction corresponding to the straight line perpendicular to the direction from the joint surface between the molds to the deepest part of the groove (the axial direction in which the joint between the molds creates a seal) is significantly larger than the expansion rate in the other directions. Therefore, by identifying this axis as the reference axis, the other two axial directions can also be identified.

[0034] In the above-described method for manufacturing a mold sealing material, the specific means of "injecting" the liquid urethane raw material composition into the groove formed on the joint surface between the molds is not particularly limited. For example, the liquid urethane raw material composition can be injected using known coating methods such as a brush, spray, or syringe.

[0035] In a mold set for molding resin in a cavity formed by joining two or more molds, when using the mold sealing material of this technology manufactured by the above manufacturing method, the mold sealing material manufactured in advance may be placed at a predetermined location on the joint surface between the molds of the mold set. However, for example, the mold sealing material of this technology may be manufactured on the mold set (on-site). Specifically, a groove is formed on the joint surface between the molds of the mold set at the position where the mold sealing material will be installed. A liquid urethane raw material composition is injected into the groove, and the joint surface with the groove is brought together with the other joint surface, and the urethane raw material composition is cured while trapped in the groove. This allows the mold sealing material of this technology to be manufactured on the mold set (on-site).

[0036] When manufacturing the mold sealing material of this technology on-site, the vertical straight line from the joint surface between the molds to the deepest part of the groove coincides with the reference axis of the manufactured mold sealing material of this technology. Therefore, even without adjusting the installation position of the mold sealing material of this technology on the joint surface between the molds, the adhesion between the joint surfaces of the molds can be effectively improved during resin molding (heating).

[0037] [Physical Properties of Mold Sealing Material] The Asker-D hardness (23°C) of the mold sealing material of this technology is preferably 30 or higher, more preferably 40 or higher, even more preferably 50 or higher, even more preferably 60 or higher, and particularly preferably 70 or higher. There is no particular upper limit to the Asker-D hardness (23°C) as long as it does not impair the purpose of this technology, but for example, it is preferably 90 or lower, and more preferably 85 or lower.

[0038] Here, "Asuka-D hardness" is measured in accordance with JIS K 6253-3. That is, in this specification, "Asuka-D hardness (23°C)" refers to the Asuka-D hardness measured in accordance with JIS K 6253-3 under room temperature conditions of 23°C.

[0039] The elongation rate (at 60°C) of the mold sealing material of this technology is preferably 15% or higher. In particular, from the viewpoint of improving the durability of the mold sealing material when resin molding is repeated using a mold set, 60% or higher is preferred, and 80% or higher is more preferred. Furthermore, there is no particular upper limit to the elongation rate (at 60°C) of the mold sealing material of this technology, but it can be adjusted to ranges such as 130% or less, 110% or less, or 100% or less.

[0040] Here, the durability of the mold sealing material refers to the durability against breakage, etc., that may occur in the sealing layer when a sealing layer made of the mold sealing material is provided on the joint surface between molds in a mold set, and when resin is molded using the said mold set.

[0041] Further, in the mold sealing material of the present technology, the elongation rate (23°C) is preferably 15% or less, more preferably 13% or less, and even more preferably 10% or less. Also, the lower limit of the elongation rate (23°C) of the mold sealing material of the present technology is not particularly limited.

[0042] Here, the "elongation rate" is measured in accordance with JIS K 6400-5. That is, in this specification, the "elongation rate (60°C)" refers to the elongation rate measured in accordance with JIS K 6400-5 under the condition of 60°C. Also, the "elongation rate (23°C)" refers to the elongation rate measured in accordance with JIS K 6400-5 under the condition of 23°C (room temperature).

[0043] In the mold sealing material of the present technology, it is preferable that the elongation rate (60°C) is larger than the elongation rate (23°C). In particular, from the viewpoint of improving the durability of the mold sealing material when resin molding using a mold set is repeated, the difference between the elongation rate (60°C) and the elongation rate (23°C) is preferably 40 percentage points or more, more preferably 45 percentage points or more, and even more preferably 50 percentage points or more.

[0044] Also, in the mold sealing material of the present technology, when the elongation rate (60°C) is larger than the elongation rate (23°C), it is preferable that the elongation rate (60°C) is 10% or more. When the mold sealing material of the present technology is heated (for example, heated from 23°C to 60°C), the elongation rate in the length direction increases. In this case, the elongation rate (60°C) may be 20% or more, 40% or more, 60% or more, 80% or more. Also, in this case, the upper limit of the elongation rate (60°C) is not particularly limited, but can be adjusted to a range such as 130% or less, 110% or less, 100% or less, etc.

[0045] The tensile strength (23°C) of the mold sealing material of the present technology may be adjusted to 20 MPa or more, preferably 30 MPa or more, more preferably 40 MPa or more, and even more preferably 50 MPa or more. By adjusting the tensile strength (23°C) to this range, it becomes easier to improve the durability of the mold sealing material.

[0046] Further, the tensile strength (60°C) of the mold sealing material of the present technology is preferably 1 MPa or more, more preferably 3 MPa or more, still more preferably 6 MPa or more, and particularly preferably 8 MPa or more. Also, the upper limit of the tensile strength (60°C) of the mold sealing material of the present technology is not particularly limited, but it can be adjusted to a range such as 20 MPa or less, 15 MPa or less, 10 MPa or less, etc.

[0047] Here, the "tensile strength" is measured in accordance with JIS K 6400-5. That is, in this specification, the "tensile strength (23°C)" refers to the tensile strength measured in accordance with JIS K 6400-5 under the condition of 23°C which is normal temperature condition. Also, the "tensile strength (60°C)" refers to the tensile strength measured in accordance with JIS K 6400-5 under the condition of 60°C.

[0048] The static friction force (23°C) of the mold sealing material of the present technology is preferably 5 N or less, more preferably 3 N or less, and particularly preferably 1 N or less. Also, the lower limit of the static friction force of the mold sealing material of the present technology is not particularly limited.

[0049] Here, the "static friction force" is measured in accordance with JIS K 7125. That is, in this specification, the "static friction force (23°C)" refers to the static friction force measured in accordance with JIS K 7125 under the condition of 23°C which is normal temperature condition.

[0050] The dynamic friction force (23°C) of the mold sealing material of the present technology may be preferably adjusted to 5 N or less, more preferably 2 N or less, and still more preferably 1 N or less. Also, the lower limit of the dynamic friction force of the mold sealing material of the present technology is not particularly limited. By adjusting the dynamic friction force within this range, it becomes easier to improve the durability of the mold sealing material.

[0051] Here, the "dynamic friction force" is measured in accordance with JIS K 7125. That is, in this specification, the "dynamic friction force (23°C)" refers to the dynamic friction force measured in accordance with JIS K 7125 under the condition of 23°C which is normal temperature condition.

[0052] The mold sealing material of this technology may be prepared to have a static compression strain (60°C) of preferably 15% or less, more preferably 13% or less. Furthermore, there is no particular lower limit to the static compression strain (60°C) of the mold sealing material of this technology. The durability of the mold sealing material can also be improved by adjusting the static compression strain (60°C) to this range.

[0053] The static compression strain (23°C) of the mold sealing material of this technology is preferably 10% or less, more preferably 8% or less, and even more preferably 5% or less. Furthermore, there is no particular lower limit to the static friction force (23°C) of the mold sealing material of this technology.

[0054] Here, "static compression strain" is measured in accordance with JIS K 6400-2. That is, in this specification, "static compression strain (60°C)" refers to the static compression strain measured in accordance with JIS K 6400-2 under 60°C conditions. Also, "static compression strain (23°C)" refers to the static compression strain measured in accordance with JIS K 6400-2 under 23°C (room temperature) conditions.

[0055] [Urethane Resin] The "urethane resin" contained in the mold sealing material of this technology possesses the characteristics of the mold sealing material of this technology described above. That is, the above urethane resin also has a specific reference axis among the three mutually orthogonal axis directions that has an expansion rate that is a certain amount greater than the expansion rate due to temperature changes in the other two axis directions. More specifically, the urethane resin of this technology has a reference axis among the three mutually orthogonal axis directions in which the expansion rate shown in the following formula (1) is 0.60% or more, and is more than twice the expansion rate in the other two axis directions.

[0056]

[0057] The method for manufacturing the urethane resin of this technology is not particularly limited. For example, it can be suitably manufactured using a method similar to the example of the method for manufacturing the mold sealing material described above. Furthermore, by synthesizing the urethane resin of this technology using the raw materials of the "urethane resin" contained in the mold sealing material of this technology described above, it is possible to suitably prepare a urethane resin having a reference axis whose expansion rate is by a certain amount greater than the expansion rates of the other two axes among the three mutually orthogonal axes. In addition, physical properties such as Asuka-D hardness (23°C) and elongation (60°C) can be efficiently adjusted to the aforementioned suitable range.

[0058] [Mold Set] Next, a mold set to which the mold sealing material of this technology is applied will be described. The mold sealing material of this technology is used in a mold set in which resin is molded in a cavity formed by joining two or more molds together, by being installed on at least one of the joining surfaces between the two or more molds to form a sealing layer.

[0059] Furthermore, in the above-mentioned mold set, when installing the mold sealing material of this technology on the joint surfaces of the molds, the adhesion between the joint surfaces can be improved by aligning the reference axis of the mold sealing material of this technology with the direction normal to the joint surfaces of the molds.

[0060] Here, the mold set in which the mold sealing material of this technology may be used is not particularly limited as long as it molds resin in a cavity formed by interlocking two or more molds, and any shape or interlocking method can be adopted. Furthermore, "interlocking two or more molds" means, for example, that if the interlocking molds consist of a mold having a concave shape and a mold having a convex shape, the number of molds having concave shapes and molds having convex shapes may be the same or different. For example, the combination may consist of a mold having one concave shape and a mold having one convex shape, or it may consist of a combination where one mold having multiple concave shapes is paired with multiple molds having one convex shape. Alternatively, it may consist of multiple molds having one concave shape paired with multiple molds having convex shapes. In this specification, the terms "concave shape" and "convex shape" are used to clarify that the molds can interlock with each other in the mold set, but these molds are not limited to the shapes of "concave shape" or "convex shape".

[0061] In the above mold set, the seal layer formed by installing the mold seal material of this technology may be provided on at least one of the joining surfaces of two or more molds. For example, if the mating molds consist of a combination of a mold having a concave shape and a mold having a convex shape, the seal layer may be provided on the joining surface of the concave mold, or on the joining surface of the convex mold, or on both the joining surface of the concave mold and the joining surface of the convex mold. Depending on the molding conditions of the resin using the mold set and the physical properties of the resin to be molded, the mold seal material of this technology can be installed at any position in the mold set to form the seal layer.

[0062] Here, the joint surfaces between molds on which the seal layer formed by the mold sealing material of this technology is provided are not limited to the outer edges of cavities formed by joining two or more molds together. For example, joint surfaces between molds are also formed in the areas of holes provided in the mold to form through-holes in the resin molded product (these holes are usually located inside the cavity, etc.). Therefore, the mold sealing material of this technology can also be installed on such joint surfaces to form a seal layer.

[0063] In the above mold set, the interlocking molds may be connected in a manner that allows them to be opened and closed through an opening and closing mechanism. When this configuration is adopted for the mold set, resin can be injected from any direction into the opening of the mold (open state) that constitutes the mounting surface, and after the resin has been injected, the other mold can be interlocked (closed state) by methods such as rotation, thus efficiently injecting resin into the cavity. It can be suitably used as a mold, especially when using foamed resin.

[0064] Here, the "opening and closing mechanism" is not particularly limited as long as it can operate to open and close the molds together. As an opening and closing mechanism, for example, a connecting member such as a hinge may be used to connect the molds so that they can rotate together. In this case, by rotating one mold relative to one mold that constitutes the mounting surface when the mold set is placed, the molds can be brought into contact with each other, forming a cavity for molding resin.

[0065] In the above mold set, the joining surfaces of the interlocking molds may be formed at an inclination with respect to the mounting surface on which the mold set is placed. For example, if the interlocking molds are connected so as to be openable and closable through an opening and closing mechanism, forming the joining surfaces at an inclination with respect to the mounting surface on which the mold set is placed, on a mold set that is rotatably mounted via a connecting member such as a hinge, allows for suitable interlocking of the molds when the molds are rotated and enables suitable opening and closing of the molds.

[0066] In other embodiments, the opening and closing of the molds may be performed not by an opening and closing mechanism using a connecting member such as a hinge, but by an opening and closing mechanism equipped with a reciprocating mechanism such as a sliding mechanism. In this case, the opening and closing operations of the molds (mold opening, mold closing) are performed by the sliding mechanism or the like.

[0067] The mold set may have grooves on the surface of the joint between the molds at positions where the mold sealing material of this technology is installed to form a sealing layer. This increases the contact area between the sealing layer of the mold sealing material of this technology and the mold per unit area of ​​the joint surface of the molds, thereby improving the adhesive strength between the sealing layer and the mold. In addition, as long as it does not impair the purpose of this technology, a portion of the sealing layer may protrude from the groove and be formed on the surface of the joint.

[0068] In particular, when manufacturing the mold sealing material of this technology on-site on the surface of the joint between molds in a mold set, the liquid urethane raw material composition is applied in a low viscosity state before the reaction in which the urethane resin is synthesized is completed. Therefore, by providing a groove on the surface of the joint between molds at the position where the mold sealing material is to be manufactured, the groove can suitably hold the liquid urethane raw material composition injected by means of application or other means. Furthermore, by joining the joint surface in which the groove is formed with other joint surfaces and curing the urethane raw material composition while it is trapped in the groove, the mold sealing material of this technology can be suitably manufactured.

[0069] Furthermore, as mentioned above, when manufacturing the mold sealing material of this technology on-site on grooves provided on the surface of the joint surfaces between molds in a mold set, the vertical straight line from the joint surfaces between the molds to the deepest part of the groove coincides with the reference axis of the manufactured mold sealing material of this technology. Therefore, even if the adjustment work for the installation position of the mold sealing material of this technology on the joint surfaces between the molds is omitted, the adhesion between the joint surfaces of the molds can be effectively improved during resin molding (heating).

[0070] Furthermore, since the mold sealing material of this technology can control the direction of expansion in response to heating in the direction of the reference axis, in a mold set in which grooves are formed on the joining surfaces of molds, by positioning the mold sealing material so that its reference axis coincides with a straight line perpendicular to the direction from the joining surface to the deepest part of the groove, the load generated by expansion on the joining surface between the mold sealing material and the groove during heating such as molding can be reduced.

[0071] Furthermore, as the liquid urethane raw material composition hardens within the groove, the adhesive strength developed during the hardening process allows the seal layer to adhere more effectively to the surface within the groove. It should be noted that the seal layer provided in this mold set is not formed with the intention of becoming part of the molded product; therefore, even if grooves are provided on the joint surface of the mold, it does not affect the shape of the resin molded product manufactured using this mold set.

[0072] In the mold set of this technology, the shape of the groove formed on the joining surfaces of the molds is not particularly limited. For example, the cross-sectional shape of the groove can be any shape, such as an arc shape or a polygon shape.

[0073] In the mold set of this technology, the depth and width of the grooves formed on the surface of the joining surfaces of two or more molds may be adjusted, for example, according to the properties of the liquid urethane raw material composition, within a range that can hold the urethane raw material composition. The depth of the grooves may be adjusted to, for example, 2 mm or more, 3 mm or more, 4 mm or more, etc. There is no particular upper limit to the depth of the grooves, but it can be adjusted to a range such as 5 mm or less. Here, the "depth of the grooves" refers to the maximum value of the depth relative to the joining surface.

[0074] Similarly, the width of the groove formed on the surface of the joint between two or more molds is adjusted to, for example, 2 mm or more, 4 mm or more, 6 mm or more, etc. Furthermore, there is no particular upper limit to the width of the groove, but it can be adjusted to a range such as 60 mm or less, 40 mm or less, 20 mm or less, 10 mm or less, etc. Here, the "groove width" is defined as the minimum vertical distance from one side of the groove to the other side.

[0075] Furthermore, in the mold set of this technology, the mold sealing material of this technology is installed in the groove, but the width and thickness of the mold sealing material do not necessarily match the width and depth of the groove, and the mold sealing material may be adjusted to a range larger than the above range.

[0076] Furthermore, when the mold sealing material of this technology is installed in a groove formed on the joint surface, a portion of the mold sealing material exposed from the groove opening (the exposed portion) may be raised outward from the groove opening so that it is at a higher position than the joint surface. The thickness (maximum value) of this exposed portion is not particularly limited as long as it does not impair the purpose of this technology, but for example, it may be in the range of 0.05 mm to 3 mm at a temperature of 23°C.

[0077] Furthermore, in the mold set of this technology, the surface of the groove in which the mold sealing material of this technology is installed may be roughened. By roughening the surface, the surface area per unit area of ​​the surface where the mold sealing material and the mold join can be further increased, thereby further improving the bonding strength between the two. This allows for the effective maintenance of the durability of the sealing layer made of the mold sealing material.

[0078] Surface roughening can be performed using any method, such as sandpaper or shot blasting. When roughening is done with sandpaper, the grit size of the sandpaper used should be, for example, #100 to #180. After the surface roughening treatment, it is preferable to avoid touching the roughened surface.

[0079] In the mold set of this technology, the groove for installing the mold sealing material of this technology is provided on the surface of the joint between the molds. This groove may be provided directly on the components that make up the mold, or it may be provided on the surface of the joint formed by filling the surface of the components that make up the mold with a metal repair agent (resin putty), for example. When the joint is formed by filling with a metal repair agent in this way, the groove is provided on the metal repair agent.

[0080] Such metal repair agents are not particularly limited as long as they are materials that can form a specific shape at any point on the metal surface, and any resin can be suitably used in accordance with the material that makes up the mold of the mold set. For example, synthetic resins such as epoxy resins and polyester resins can be used. The hardness of these synthetic resins may be adjusted by containing any hardening agent.

[0081] The thickness of the seal layer formed by installing the mold sealing material of this technology on the joint surface between molds is not particularly limited as long as it does not impair the purpose of this technology, but for example, 0.05 mm or more is preferred, 1 mm or more is more preferred, and 2 mm or more is particularly preferred. Furthermore, there is no particular upper limit to the thickness of the seal layer, but it can be adjusted to a range such as 3 mm or less, 2 mm or less, or 1 mm or less.

[0082] Furthermore, the width of the sealing layer is not particularly limited as long as it does not impair the purpose of this technology, but can be adjusted to a range such as 2 mm or more, 4 mm or more, or 6 mm or more. The upper limit of the width can also be adjusted to a range such as 60 mm or less, 40 mm or less, 20 mm or less, or 10 mm or less. The thickness and width of the sealing layer are values ​​measured under a temperature of 23°C.

[0083] When the mold sealing material of this technology is installed in a groove formed on the joint surface between molds, the thickness of the sealing layer, including not only the portion exposed from the groove and raised higher than the joint surface but also the portion filled within the groove (maximum thickness), can be adjusted to any thickness according to the groove depth described later. For example, it can be adjusted to 2 mm or more, 3 mm or more, 4 mm or more, etc. Furthermore, there is no particular upper limit to the thickness of the sealing layer, but it can be adjusted to a range such as 5 mm or less. However, in the case of the sealing layer, it is preferable that the thickness of the portion raised higher than the joint surface be at least 0.3 mm, and more preferably 0.5 mm or more. Note that the thickness of the sealing layer is a value measured under a temperature of 23°C.

[0084] The sealing layer may be formed in an annular shape, encircling the cavity within the mold, or it may be formed with a portion of the annular shape missing. In other words, the sealing layer may be positioned to surround the resin molded product within the cavity, or it may be positioned only on a portion of the resin molded product.

[0085] Figure 2 is a perspective view of an example of a mold set in which the mold sealing material of this technology is installed on the joint surfaces of the molds. The mold set 100 shown in the figure consists of two molds 101 and 102. In the mold set 100 shown in Figure 2, the mold 101 that constitutes the mounting surface when the mold set 100 is placed has a concave shape, and the other mold 102 has a convex shape. The concave mold 101 and the convex mold 102 are connected via a hinge 103 so as to be openable and closable as an opening and closing mechanism. As a result, by rotating the convex mold 102 relative to the concave mold 101 that constitutes the mounting surface when the mold set 100 is placed, the molds can be mated together to form a cavity 104 for molding resin.

[0086] Figure 3 is a cross-sectional view taken from the direction indicated by the arrow in Figure 2, in the XY plane in Figure 2 (a cross section perpendicular to the mounting surface 108 on which the mold set 100 is placed), when the convex mold 102 is rotated to fit together the concave mold 101. By fitting together the concave mold 101 and the convex mold 102, a cavity 104 for molding resin is formed. At this time, a seal layer 106 formed by the mold seal material of this technology is provided on the joint surface 105 between the molds.

[0087] In the example of the mold set shown in Figure 3, a groove 107 is formed on the surface of the joining surface 105. When a groove is formed on the joining surface of two molds, the adhesion between the joining surfaces can be improved by installing the mold seal material so that the reference axis of the mold seal material of this technology coincides with a straight line perpendicular to the groove from the joining surface to the deepest part of the groove. Furthermore, when manufacturing the mold seal material of this technology on-site on the surface of the joining surface 105 of the molds in the mold set, the liquid urethane raw material composition is applied in a low viscosity state before the reaction in which the urethane resin is synthesized is completed. Therefore, the groove 107 can suitably hold the applied liquid urethane raw material composition. Moreover, as described above, the mold seal material of this technology can be suitably manufactured by curing the joint surface 105 with the groove 107 in place together with other joining surfaces, with the urethane raw material composition trapped in the groove.

[0088] Furthermore, a release agent may be applied to the surface of the seal layer 106. Here, the release agent is an agent used to efficiently remove the resin molded product from the mold set 100. By applying such a release layer to the surface of the seal layer 106, adhesion between the seal layer (mold seal material) 106 and the resin molded product is suppressed, and the resin molded product can be efficiently removed from the mold set 100. As the release agent, a known release agent used during the molding of resin molded products can be used. For example, if the resin molded product is made of urethane resin foam, a known release agent used during the molding of the urethane resin foam (for example, product name "M975", product name "T-626", both manufactured by Chukyo Oil & Fat Co., Ltd.) can be used.

[0089] In the examples shown in Figures 2 and 3, the seal layer 106 is provided on a concave mold 101. However, as mentioned above, depending on the molding conditions of the resin using the mold set and the physical properties of the resin to be molded, the seal layer may be provided on the joint surface of a convex mold, or the seal layer may be provided on both the joint surface of the concave mold and the joint surface of the convex mold.

[0090] Figure 3 shows an example of a mold set in which grooves are formed on the joining surfaces of the molds. Even with a mold set in which grooves are formed on the joining surfaces of the molds, the adhesion between the joining surfaces of the molds can be improved by setting the reference axis of the mold sealing material of this technology to coincide with the direction normal to the joining surfaces of the molds. Also, Figure 3 shows an example in which excess burrs of the sealing layer related to the mold sealing material are removed by the <finishing> process of the sealing layer formation method described later, so that the joining surfaces of the molds and the surface of the sealing layer that joins to the molds coincide. However, the shape of the sealing layer can be arbitrarily adjusted according to its purpose.

[0091] Figure 4 is an enlarged view of the vicinity of the mold sealing material 106 installed in the groove 107 formed in the joint surface 105 between the molds of the mold set 100 in Figure 3 (within the frame enclosed by the dotted line in Figure 3). In the figure, point a indicates the deepest part of the groove from the joint surface between the molds, and line A indicates a straight line perpendicular to the joint surface between the molds and the deepest part of the groove. When the mold sealing material 106 of this technology is installed so that its reference axis coincides with line A, the mold sealing material 106 expands significantly in the direction of the reference axis when heated, such as during resin molding, as shown in the example in Figure 1, thereby improving the adhesion between the joint surfaces of the molds.

[0092] Figure 5 shows a modified example of a mold set in which the mold sealing material of this technology is installed, in which the groove for installing the mold sealing material of this technology is provided on the surface of the joint surface formed by filling the surface of the member constituting the mold with a metal repair agent (resin putty). In Figure 5, as in Figure 4, it can be confirmed that a groove 107 is formed in the joint surface 105 formed by filling with a metal repair agent (resin putty) 109 in the area corresponding to the vicinity of the mold sealing material 106 installed in the groove 107 formed in the joint surface 105 of the mold set 100 in Figure 3 (within the frame enclosed by the dotted line in Figure 3). In this case as well, the adhesion between the joint surfaces of the molds can be improved by installing the mold sealing material 106 of this technology so that its reference axis coincides with a straight line A in the vertical direction from the joint surface of the molds to the deepest part of the groove.

[0093] In the example shown in Figure 5, the cavity 104 of the mold set is curved convexly with respect to the joint surface 105 between the molds. More specifically, the cavity-side end of the joint surface 105 is curved convexly, and the cavity-side tip of the metal repair agent (resin putty) 109 protrudes further towards the cavity 104 than the tip of the mold 101, resulting in a so-called under-shape. Even in this configuration, the mold sealing material 106 of this technology can control the expansion direction during heating, such as when molding resin using the mold set, thereby reducing the load on the metal repair agent (resin putty) 109. In particular, even when the distance from the end of the groove 107 to the cavity-side tip of the metal repair agent (resin putty) 109 is short, such as when the groove 107 is provided near the cavity 104, the mold sealing material of this technology can be suitably used as a sealing layer.

[0094] [Method for Forming the Seal Layer] Next, a specific method for providing a seal layer made of the mold seal material of this technology on the joint surfaces of the molds will be described. This is an example of how to install the mold seal material of this technology on the joint surfaces of the molds of a mold set, and describes an example where the mold seal material of this technology is manufactured on-site on the surface of grooves formed on the joint surfaces of the molds. In this example as well, any necessary steps may be omitted or added as needed.

[0095] <Mold Cleaning> First, it is preferable to clean the molds that constitute the mold set on which the sealing layer is provided. The molds can be cleaned using any solvent or dry ice appropriate to the resin being molded, under known cleaning conditions.

[0096] <Application of mold release agent> Next, a mold release agent is applied to the surface of each mold constituting the cavity using a brush or the like (example of application). As for the mold release agent, for example, when molding polyurethane foam using a mold set, a known mold release agent known as a urethane mold release agent can be suitably used.

[0097] <Adding Legs> Next, the surface of the joint surface of the mold on which the mold sealing material is to be installed may be roughened. Roughening increases the surface area of ​​the joint between the mold sealing material and the mold, which can improve the joint strength between the two. The roughening treatment can be carried out using any method, such as sandpaper. When roughening is done with sandpaper, the grit size of the sandpaper used should be, for example, #100 to #180. After roughening, it is preferable to avoid touching the roughened surface.

[0098] <Sealant Application> Next, a first liquid (liquid A) containing a polyol component and a second liquid (liquid B) containing a polyisocyanate component are mixed and stirred to produce a liquid urethane raw material composition. The stirring time at this time is not particularly limited as long as the conditions allow for sufficient stirring of liquids A and B. For example, any time can be adjusted as the stirring time, such as 5 to 20 minutes. The obtained urethane raw material composition is applied to predetermined locations such as grooves on the joint surfaces of the molds. Known coating methods such as brushes, sprays, and syringes can be used to apply the urethane raw material composition.

[0099] <Primary Curing> The urethane raw material composition applied to a predetermined location on the joint surface is allowed to cure for a certain period of time, allowing the urethane resin synthesis reaction to proceed and complete hardening. At this time, the joint surface of the mold set in which the groove is formed is brought together with other joint surfaces, and the urethane raw material composition is cured while being confined within the groove, thereby suitably producing the mold sealing material of this technology. The curing time is not particularly limited, but for example, it is about 1 to 3 hours.

[0100] <Finishing> After curing, it is preferable to shape the seal layer of the mold seal material manufactured using this technology by deburring. The method of deburring is not particularly limited, and any method can be used. For example, the shape of the mold seal material can be shaped by removing excess burrs from the mold seal material using any cutting tool such as a chisel or cutter.

[0101] <Secondary Curing> After deburring, it is preferable to cure the mold for a certain period of time. The curing time is not particularly limited, but for example, it is about the same amount of time as the primary curing (for example, about 1 to 3 hours).

[0102] <Confirmation of Mold Fitting> It is preferable to confirm whether the seal layer formed above is formed in a suitable position on the joining surface of the molds. This confirmation can be performed by any method, but for example, by applying red lead to the seal layer formed on the joining surface of the molds and then fitting the molds together, it is possible to confirm whether the seal layer is formed in the desired position.

[0103] <Cleaning> Finally, remove any excess mold release agent or red lead adhering to the seal layer. The method of removal is not particularly limited, and any method can be used. For example, these can be suitably removed with a solvent appropriate to the mold release agent.

[0104] Furthermore, when the resin molded product formed by the mold set is made of polyurethane foam, etc., it is preferable to apply a release agent to the surface of the seal layer in order to suppress the adhesion of a part of the foam to the seal layer. As the release agent, the known release agents described above may be used.

[0105] Furthermore, the sealing layer may be provided with grooves or slits, if necessary, to allow gas from inside the cavity to escape to the outside of the mold.

[0106] The mold sealing material of this technology can be removed from the groove as needed, and new mold sealing material can be installed on the joint surface between molds. For example, if the number of shots of resin molded products produced by the mold set exceeds a certain number, or if a predetermined period of time has elapsed, the mold sealing material installed in the groove can be replaced with new mold sealing material as appropriate.

[0107] [Manufacturing of resin molded products] By the above method, a mold set in which the mold sealing material of this technology is installed on the joint surfaces of the molds can improve the adhesion between the joint surfaces of the molds.

[0108] The resins that can be molded using the molds of this technology are not particularly limited, and any resin can be suitably molded to produce resin molded products. For example, if the mold set of this technology is configured such that the interlocking molds are connected to each other in an openable and closable manner through an opening and closing mechanism, the ease of injecting resin into the cavity within the mold makes it particularly suitable for molding foamed resins. Examples of foamed resin molded products in this case include urethane foam molded using urethane resin, thermoplastic resin foam formed using thermoplastic resin, and thermosetting resin foam molded using thermosetting resin. In other embodiments, the mold set of this technology can also be used for molding non-foamed resins.

[0109] When molding foamed resin using the mold set of this technology, a gas passage may be provided to allow gas generated by foaming to escape from the cavity formed by joining the molds to the outside of the mold. The passage in this case is not particularly limited, but for example, a groove may be provided in the mold sealing material installed on the joint surface between the molds, leading from the inside of the cavity to the outside of the mold. When providing such a groove that serves as a gas passage, it may be designed to cross from the inside of the cavity to the outside of the mold. In this case, it is preferable that the groove that serves as the gas passage is not created by completely cutting through the mold sealing material in the thickness direction, but rather by partially removing the mold sealing material in the thickness direction in an arbitrary shape such as a concave shape. Alternatively, the above groove may be provided at multiple locations on the mold sealing material.

[0110] Furthermore, in the mold set of this technology, by installing the mold sealing material of this technology at predetermined locations on the joint surface (locations where the gap between the cavity and the sealing layer is greater than a certain distance), the amount of burrs formed around the resin molded product can be kept to a minimum.

[0111] Furthermore, this technology can also be configured as follows: [1] A mold sealing material containing urethane resin, having a reference axis in which the expansion rate shown by the following formula (1) is 0.60% or more and is at least twice the expansion rate in the other two axes, among three mutually orthogonal axes. [2] The mold sealing material according to [1], wherein the Asker D hardness (23°C) is 30 or higher. [3] The mold sealing material according to [1] or [2], wherein the elongation (60°C) is 40% or higher. [4] The mold sealing material according to any one of [1] to [3], wherein the elongation (60°C) is greater than the elongation (23°C), and the elongation (60°C) is 10% or higher. [5] The mold sealing material according to any one of [1] to [4], wherein the tensile strength (23°C) is 20 MPa or higher. [6] The mold sealing material according to any one of [1] to [5], wherein the static friction force (23°C) is 5 N or less. [7] The mold sealing material according to any one of [1] to [6], wherein the kinetic friction force (23°C) is 5 N or less. [8] The mold sealing material according to any one of [1] to [7], wherein the static compression strain (60°C) is 15% or less. [9] A mold sealing material according to any one of [1] to [8], wherein the urethane resin has a polycaprolactone structure.

[10] A mold set for molding resin in a cavity formed by joining two or more molds, wherein a groove is formed on at least one of the joining surfaces of the two or more molds, and a mold sealing material according to any one of [1] to [9] is installed in the groove such that a straight line perpendicular to the direction from the joining surface to the deepest part of the groove coincides with the reference axis.

[11] The mold set according to

[10] , wherein the joining surface is formed at an inclination with respect to the mounting surface on which the mold set is placed.

[12] The mold set according to

[10] or

[11] , wherein the surface of the groove is subjected to a roughening treatment.

[13] The mold set according to any one of

[10] to

[12] , wherein the resin is a foaming resin.

[14] The mold set according to

[13] , wherein the foaming resin is a urethane resin.

[15] A mold set according to any one of

[10] to

[14] , wherein the two or more molds are connected to each other so as to be openable and closable through an opening and closing mechanism.

[16] A method for manufacturing a resin molded product using a mold set according to any one of

[10] to

[15] .

[17] A method for manufacturing a mold seal material according to any one of [1] to [9], comprising the steps of: injecting a liquid urethane raw material composition into a groove formed in at least one of the joining surfaces of two or more molds; and curing the joining surface in which the groove is formed with the other joining surfaces, thereby trapping the urethane raw material composition within the groove.

[18] A raw material composition for a mold seal material according to any one of [1] to [9], comprising a first liquid containing a polyol component and a second liquid containing a polyisocyanate component, to be applied to at least one of the joining surfaces of two or more molds in a mold set for molding resin in a cavity formed by joining two or more molds.

[19] A urethane resin having a reference axis in which, among three mutually orthogonal axial directions, the expansion rate shown by the following formula (1) is 0.60% or more and is at least twice the expansion rate in the other two axial directions.

[20] The urethane resin according to

[19] , wherein the Asker D hardness (23°C) is 30 or higher.

[21] The urethane resin according to

[19] or

[20] , wherein the elongation (60°C) is 40% or higher.

[22] The urethane resin according to any one of

[19] to

[21] , wherein the elongation (60°C) is greater than the elongation (23°C), and the elongation (60°C) is 10% or higher.

[23] The urethane resin according to any one of

[19] to

[22] , wherein the tensile strength (23°C) is 20 MPa or higher.

[24] The urethane resin according to any one of

[19] to

[23] , wherein the static friction force (23°C) is 5 N or less.

[25] The urethane resin according to any one of

[19] to

[24] , wherein the kinetic friction force (23°C) is 5 N or less.

[26] The urethane resin according to any one of

[19] to

[25] , wherein the static compression strain (60°C) is 15% or less.

[27] The urethane resin according to any one of

[19] to

[26] , wherein the urethane resin has a polycaprolactone structure.

[0112] The present technology will be described in more detail below using examples. However, the present technology is not limited in any way to the examples shown below.

[0113] [Raw Materials] ◆First liquid (Solution A) containing polyol components ・Polyester polyol (polycaprolactone polyol) / (A-1) / Appearance (room temperature): liquid, viscosity 10 mPa·s, acid value 0.50 KOH mg / g, hydroxyl value 305.6 KOH mg / g, number of functional groups 3, number average molecular weight 550 ・Polycarbonate polyol / (A-2) / number average molecular weight 1000 ・Polyether polyol (polypropylene oxide with ethylene oxide at the end) / (A-3) / hydroxyl value 35 mg KOH / g, number of functional groups 3, number average molecular weight 5000 ・Polyfunctional polyether polyol / (A-4) / hydroxyl value 445 mg KOH / g, viscosity 8,000 (mPa·s at 25℃) ◆Second liquid (Solution B) containing polyisocyanate components • Polyisocyanate: Polymeric MDI (crude MDI) / (B-1) / NCO%: 34% • Polyisocyanate: Polymeric MDI (crude MDI) / (B-2) / NCO%: 31.3% • Polyisocyanate: Polymeric MDI (crude MDI) / (B-3) / NCO%: 23%

[0114] [Manufacturing of mold sealing material] To evaluate the expansion rate of the mold sealing material, an evaluation piece was first prepared by using a mold set in which two molds interlock to form a cavity with a height of 20 mm on a bottom surface measuring 200 mm in length and 200 mm in width. The mold sealing material was then prepared by cutting it so that the length and width were both 30 mm, while maintaining the axis corresponding to the height direction of the cavity (maintaining the length of 20 mm in the height direction derived from the mold).

[0115] Furthermore, for evaluating the physical properties of the mold sealing material, an evaluation piece was prepared using a mold set in which two molds interlock to form a cavity with a height of 10 mm on a base surface measuring 200 mm in length and 200 mm in width. Subsequently, the obtained mold sealing material was prepared by cutting it to a length of 100 mm and a width of 4 mm while maintaining the axis corresponding to the height direction of the cavity.

[0116] To produce the mold sealing material, the inside of the cavity of the mold set was cleaned using a solvent (solvent name NMP, manufactured by Sanwa Yuka Kogyo Co., Ltd.) or dry ice. Then, a mold release agent (product name M-975, manufactured by Chukyo Yushi Co., Ltd.) was applied to the surface of the cavity. After that, the surface of the cavity was roughened using sandpaper (#60).

[0117] A liquid urethane raw material composition was produced by mixing 28 g of a first liquid (liquid A) containing a polyol component and 21 g of a second liquid (liquid B) containing a polyisocyanate component in the combinations shown in Table 1, and stirring for 10 minutes. The obtained urethane raw material composition was injected into the cavity of the mold set by coating under room temperature conditions of 25°C, the molds of the mold set were mated together, and the urethane raw material composition was cured while trapped in the grooves to produce a mold sealing material. The coating time for the urethane raw material composition was 5 minutes. Coating was performed using a spatula or syringe.

[0118] Subsequently, the mold in which the mold sealant had been cured was allowed to cure for two hours after application. Then, excess burrs were removed using a cutter, and the shape of the mold sealant was refined. After the burr removal, the mold was allowed to cure for another two hours. As described above, the obtained mold sealant was cut out so that the length and width were 30 mm, maintaining the axis corresponding to the height direction of the cavity, and each piece was used as an evaluation piece for evaluating the expansion rate of each mold sealant. Similarly, for the evaluation pieces for physical property evaluation, the obtained mold sealant was cut out so that the length was 100 mm and the width was 4 mm, maintaining the axis corresponding to the height direction of the cavity, and each piece was used as an evaluation piece for each mold sealant.

[0119]

[0120] [Evaluation of Expansion Rate of Mold Sealing Materials] For each evaluation piece obtained for evaluating the expansion rate of the mold sealing material, the "axial length at the initial stage (23°C)" was measured at three points each in the height direction (corresponding to the depth direction of the groove) and in the two axes perpendicular to the height direction (vertical and horizontal directions) under the condition of 23°C. Similarly, the "axial length at the time of heating (60°C)" was measured at three points each in the height direction (corresponding to the depth direction of the groove) and in the two axes perpendicular to the height direction (vertical and horizontal directions) under the condition of 60°C.

[0121] The expansion rate was calculated using formula (1) above, based on the average values ​​of the measurement results for the "axial length at initial temperature (23°C)" and the "axial length during heating (60°C)" for each of the above-mentioned mold sealing materials. The results are shown in Table 2.

[0122]

[0123] For the mold sealing materials of Examples 1 to 3, the expansion rate in the height direction is more than twice the expansion rate in the other two axial directions (vertical and horizontal directions), and it can be confirmed that this expansion rate is 0.60% or more. For these mold sealing materials, by using the height direction as the reference axis, it can be confirmed that the adhesion between the joint surfaces of the molds can be improved by installing the mold sealing material so that the direction of the reference axis coincides with the direction normal to the joint surface between the molds.

[0124] Furthermore, while the mold sealing materials of Examples 1 to 3 can control the direction of expansion with heating, mainly in the height direction, it can be confirmed that the mold sealing materials of the comparative examples cannot control the direction of expansion with heating in a specific direction. For this reason, even if the mold sealing material of this technology is installed in a groove provided on the surface of a joint formed by filling the surface of a component constituting the mold with a metal repair agent (resin putty), the direction of expansion during heating, such as when molding resin using a mold set, can be controlled, thereby reducing the load on the metal repair agent. In particular, even if the metal repair agent takes an under-shape as shown in Figure 5 due to the shape of the cavity, the load on the metal repair agent can be reduced by using the mold sealing material of this technology as a sealing layer.

[0125] [Evaluation of Physical Properties of Mold Sealing Materials] Next, using the evaluation pieces obtained above for evaluating the physical properties of the mold sealing materials of Examples 1 to 3, the physical properties of each mold sealing material were measured in accordance with the following standards. The measurement results are shown in Table 3. ・Asuka-D hardness (23°C): JIS K 6253-3 ・Elongation (23°C) and elongation (60°C): JIS K 6400-5 ・Tensile strength (23°C) and tensile strength (60°C): JIS K 6400-5 ・Static friction force (23°C) and kinetic friction force (23°C): JIS K 7125 ・Static compression strain (23°C) and static compression strain (60°C): JIS K 6400-2

[0126]

[0127] From the obtained physical properties, it can be confirmed that the mold sealing materials of Examples 1 to 3 possess practical functionality as a sealing layer even when installed on the joint surfaces of molds in a mold set and used as a sealing layer. Furthermore, it can be expected that the durability of the mold sealing material can be ensured when resin molding is repeatedly performed using the mold set.

[0128] [Confirmation of the practicality of the mold sealing material] The mold sealing material of Example 1 was manufactured on the surface of the joint between molds of a mold set equipped with a configuration in which molds are rotatably connected to each other using connecting members such as hinges, using the groove formed on the joint surface of the molds as the mold, under the manufacturing conditions of the mold sealing material described above. As a result, the vertical straight line from the joint surface of the molds toward the deepest part of the groove coincides with the reference axis of the manufactured mold sealing material.

[0129] Using a mold set in which mold seals are installed on the joint surfaces of the molds obtained above, we confirmed that the seals possess practical functionality as a sealing layer by manufacturing molded products of urethane resin, a foamed resin, under the following conditions. Furthermore, we confirmed that the durability of the seals as a mold sealing material is also ensured by repeatedly performing resin molding using the mold set.

[0130] <Molding conditions> - Pressure during molding: 3 MPa

[0131] <Resin raw materials used for molding> ◆First liquid containing polyether polyol as the polyol component ◆Second liquid containing monomeric MDI as the polyisocyanate component ◆Foaming agent: Water ◆Mixing ratio (mass ratio) Polyether polyol: Polymeric MDI = 65:35

[0132] 100 Mold set 101 Concave mold 102 Convex mold 103 Opening / closing mechanism (hinge) 104 Cavity 105 Joining surface 106 Mold sealing material (sealing layer) 107 Groove 108 Mounting surface 109 Metal repair agent (resin putty) A A straight line perpendicular to the joint surface of the molds from the deepest part of the groove a The deepest part of the groove from the joint surface of the molds

Claims

1. A mold sealing material containing urethane resin, having a reference axis in which, among three mutually orthogonal axial directions, the expansion rate shown by the following formula (1) is 0.60% or more, and is at least twice the expansion rate in the other two axial directions.

2. The mold sealing material according to claim 1, wherein the Asker D hardness (23°C) is 30 or higher.

3. A mold set for molding resin in a cavity formed by joining two or more molds, wherein a groove is formed on at least one of the joining surfaces of the two or more molds, and the mold sealing material according to claim 1 or claim 2 is installed in the groove such that a straight line perpendicular to the direction from the joining surface to the deepest part of the groove coincides with the reference axis.

4. A method for manufacturing a mold seal material according to claim 1 or claim 2, comprising the steps of: injecting a liquid urethane raw material composition into a groove formed in at least one of the joining surfaces of two or more molds; and curing the joining surface in which the groove is formed with the other joining surfaces, with the urethane raw material composition trapped in the groove.

5. A urethane resin having a reference axis in which the expansion rate represented by the following formula (1) is 0.60% or more and is at least twice the expansion rates in the other two axial directions among three mutually orthogonal axial directions.

Images