Laminate and method for producing laminate

Abstract

To provide a laminate and a method for producing a laminate, capable of enhancing the bonding strength between a first layer and a second layer.SOLUTION: A laminate 11 has a first layer 12 composed of polyolefin and a second layer 13 composed of thermosetting polyurethane, laminated on the first layer 12. The first layer 12 and the second layer 13 are bonded together through a mixed layer 14 in which both components of the polyolefin constituting the first layer 12 and the thermosetting polyurethane constituting the second layer 13 are intermixed.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a resin laminate and a method for producing the laminate. [Background technology]

[0002] Generally, polypropylene is known to be a poorly adhesive resin with low adhesiveness due to its low surface free energy. When laminating another resin layer onto poorly adhesive resins such as polypropylene, a method is generally adopted in which the surface of the poorly adhesive resin is modified by plasma treatment or the like, and then the resin layer is adhered to the surface using an adhesive or the like. However, laminating a resin layer onto a poorly adhesive resin using this method requires a step of applying an adhesive, which reduces the productivity of the product.

[0003] Conventionally, an article has been proposed in which a thermoplastic polyurethane is adhered to a polypropylene surface without using an adhesive (see, for example, Patent Document 1). This article is made by subjecting the polypropylene surface to a plasma treatment, and then adhering and bonding a thermoplastic polyurethane to the surface by injection molding. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2008-531331 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the article of Patent Document 1 has a structure in which the thermoplastic polyurethane is only attached to the surface portion of the polypropylene, so there is a risk that the bonding strength between the polypropylene and the thermoplastic polyurethane is not sufficiently ensured. For this reason, there is a demand for a laminate in which a resin layer is bonded to a poorly adhesive resin with higher bonding strength without using an adhesive. [Means for solving the problem]

[0006] Various aspects of a laminate and a method for producing the laminate for solving the above problems will be described below. [Embodiment 1] A laminate comprising a first layer made of polyolefin and a second layer made of thermosetting polyurethane laminated to the first layer, wherein the first layer and the second layer are joined by a mixed layer in which both the polyolefin component constituting the first layer and the thermosetting polyurethane component constituting the second layer are mixed together.

[0007] According to the above configuration, the first layer and the second layer are bonded together by a mixed layer in which the components of the polyolefin and the thermosetting polyurethane constituting the first layer and the second layer, respectively, are mixed together. That is, the first layer and the second layer are bonded together by the mixed layer in which the components are mixed together in a complex manner. This can further increase the bonding strength between the first layer and the second layer.

[0008] [Aspect 2] A method for producing a laminate, comprising: a first layer molding step of molding a first layer made of polyolefin by injection molding; an amorphous layer forming step of forming an amorphous layer on the surface of the first layer; a mold clamping step of clamping a mold in which the first layer with the amorphous layer formed on its surface is set; and a second layer molding step of injecting a thermosetting polyurethane precursor into a cavity of the mold and hardening the precursor while allowing the precursor to permeate the amorphous layer, thereby molding a second layer made of thermosetting polyurethane.

[0009] According to the above method, the precursor of the thermosetting polyurethane permeates the amorphous layer of the first polyolefin layer while hardening, forming the second thermosetting polyurethane layer. At this time, the amorphous layer permeated with the precursor becomes a mixed layer in which both the polyolefin and thermosetting polyurethane components constituting the first and second layers, respectively, are mixed in a complex manner. Therefore, the first and second layers are integrally bonded in this mixed layer, so that the bonding strength between the first and second layers can be further increased.

[0010] [Aspect 3] The method for producing a laminate according to [Aspect 2], wherein the thickness of the amorphous layer formed in the amorphous layer forming step is 5 nm or more and 500 nm or less. According to the above method, the mixed layer bonding the first layer and the second layer to each other has a sufficient thickness, so that the bonding strength between the first layer and the second layer can be more reliably increased. Effect of the Invention

[0011] The present invention has an effect of further increasing the bonding strength between the first layer and the second layer. [Brief description of the drawings]

[0012] [Figure 1] FIG. 2 is a cross-sectional view showing an embodiment of a laminate. [Diagram 2] FIG. 2 is an enlarged view showing a main part of FIG. [Diagram 3] FIG. 4 is a cross-sectional view showing a first layer molding step. [Figure 4] FIG. 4 is a cross-sectional view showing an amorphous layer forming step. [Diagram 5] 1 is an electron microscope photograph showing a part of a first layer with an amorphous layer formed on the surface. [Figure 6] FIG. 4 is a schematic cross-sectional view showing a mold clamping process. [Figure 7] FIG. 4 is a cross-sectional view showing a second layer molding step. [Figure 8] 2 is an electron microscope photograph showing a main part of a laminate. [Figure 9] FIG. 2 is a schematic diagram showing the distribution of components in a laminate. [Figure 10] 10 is a graph showing the relationship between position and component in the laminate of FIG. 9. [Figure 11] FIG. 11 is a cross-sectional view showing a first layer molding step in a modified example. [Figure 12] 10A to 10C are cross-sectional views illustrating an amorphous layer forming step according to a modified example. [Figure 13] 13A and 13B are schematic cross-sectional views showing a mold clamping step and a second layer molding step in a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] An embodiment will now be described with reference to the drawings. <Laminate 11> As shown in Fig. 1 and Fig. 2, the laminate 11 is made of resin and is an exterior part such as a vehicle bumper. The laminate 11 includes a first layer 12, a second layer 13 laminated on the first layer 12, and a mixed layer 14 joining the first layer 12 and the second layer 13. The first layer 12 is made of polyolefin. As an example, the first layer 12 is made of polypropylene (PP). The second layer 13 is made of thermosetting polyurethane (PU). The mixed layer 14 is a layer in which both components, the polypropylene constituting the first layer 12 and the thermosetting polyurethane constituting the second layer 13, are mixed together.

[0014] <Method of manufacturing laminate 11> The method for manufacturing the laminate 11 includes a first layer molding step, an amorphous layer forming step, a mold clamping step, and a second layer molding step.

[0015] <1st layer molding process> As shown in Fig. 3, in the first layer molding step, a first layer 12 made of polypropylene is molded by injection molding. That is, molten polypropylene is injected from a cylinder (not shown) into a first cavity 16 of a first molding die 15 in a clamped state, and then cooled and solidified to mold the first layer 12. The first molding die 15 includes a fixed die 17 and a first movable die 18. After the first layer 12 is molded by the first molding die 15, the first molding die 15 is opened and the first layer 12 is removed from the first molding die 15.

[0016] <Amorphous layer formation process> As shown in Figures 4 and 5, in the amorphous layer forming step, the surface of the first layer 12 removed from the first mold 15 is modified by, for example, corona treatment or flame treatment to form an amorphous layer 19 on the surface of the first layer 12. The amorphous layer 19 is a layer in which the arrangement of the molecules and atoms constituting the first layer 12 is irregular and not constant. Figure 5 is an electron microscope photograph showing a part of the first layer 12 with the amorphous layer 19 formed on its surface. The black part in Figure 5 is the amorphous layer 19.

[0017] When performing corona treatment on the surface of the first layer 12, for example, a corona discharge surface modification device 20 is used. The thickness of the amorphous layer 19 formed on the surface of the first layer 12 by corona treatment or the like is preferably 5 nm or more and 500 nm or less, and more preferably 10 nm or more and 200 nm or less. The thickness of the amorphous layer 19 shown in FIG. 5 is about 15 nm.

[0018] <Mold clamping process> 6 and 7, in the mold clamping step, the first layer 12 with the amorphous layer 19 formed on the surface is set in a second molding die 21, which is an example of a metal mold, and then the second molding die 21 is clamped. The second molding die 21 is obtained by replacing the first movable die 18 in the first molding die 15 with a second movable die 22. Therefore, the second molding die 21 includes a fixed die 17 and a second movable die 22.

[0019] The fixed mold 17 is used in common for both the first molding mold 15 and the second molding mold 21. The second molding mold 21 is a metal mold that molds the second layer 13 so as to cover the surface of the first layer 12. In the second molding mold 21, a space 25 is formed between the surface of the first layer 12 in a second cavity 23 that is formed when the first layer 12 is clamped and a cavity surface 24 of the second movable mold 22.

[0020] <Second layer molding process> As shown in FIG. 7, in the second layer molding step, a first liquid and a second liquid, which are an example of a precursor of thermosetting polyurethane, are mixed and injected into a space 25 in a second cavity 23 of a second molding die 21 in a state in which the first layer 12 is set and the second molding die 21 is closed. The first liquid is a liquid whose main component is polyol. The second liquid is a liquid whose main component is isocyanate. In this case, the first liquid and the second liquid are preferably heated to about 50°C to 70°C before mixing. Furthermore, in this case, the second molding die 21 is preferably heated to about 60°C to 100°C beforehand.

[0021] After the first liquid and the second liquid are injected into the space 25, the second mold 21 is clamped at a constant pressure and held for about 20 to 90 seconds. As a result, the first liquid and the second liquid fill the space 25 and permeate the amorphous layer 19 on the surface of the first layer 12, and undergo a chemical reaction to harden into a thermosetting polyurethane. As a result, the laminate 11 is obtained in which the second layer 13 made of thermosetting polyurethane is molded in a state where it is integrally joined with the first layer 12. Thereafter, the second mold 21 is opened, and the laminate 11 is taken out of the second mold 21.

[0022] <Joint Portion Between First Layer 12 and Second Layer 13 in Laminate 11> Fig. 8 is an electron microscope photograph showing the junction between the first layer 12 and the second layer 13 and its surroundings in the laminate 11. It can be seen from Fig. 8 that a mixed layer 14 is formed at the position where the amorphous layer 19 was formed in the first layer 12, i.e., the junction between the first layer 12 and the second layer 13. The thickness of the mixed layer 14 shown in Fig. 8 is 150 nm to 200 nm.

[0023] Also, from Fig. 8, it can be seen that the mixed layer 14 is remarkably thicker than the amorphous layer 19 shown in Fig. 5. That is, from Fig. 8, it can be seen that when the first liquid and the second liquid permeate the amorphous layer 19 and undergo a chemical reaction to become a thermosetting polyurethane, the amorphous layer 19 and the thermosetting polyurethane mix together, increasing in volume to become the mixed layer 14.

[0024] <Component analysis of mixed layer 14> As shown in Fig. 9, the mixed layer 14 is present in the vicinity of a position of 200 nm in the laminate 11. When the components of the laminate 11 were analyzed, the results shown in Fig. 10 were obtained. The vertical positions indicated by the arrows in the schematic diagram of the laminate 11 in Fig. 9 correspond to the horizontal positions in the graph in Fig. 10.

[0025] 10, it can be seen that the mixed layer 14 existing in the vicinity of the 200 nm position in the laminate 11 contains both component A of the amorphous polypropylene layer 19 constituting the first layer 12 and component B of the thermosetting polyurethane. Note that component B is nitrogen. Nitrogen is contained in thermosetting polyurethane but not in polypropylene, so it can be said to be a thermosetting polyurethane.

[0026] <Operation of the embodiment> In the laminate 11, the polypropylene constituting the first layer 12 and the thermosetting polyurethane constituting the second layer 13 are bonded together by a mixed layer 14 in which both of these components are mixed together. That is, the first layer 12 and the second layer 13 are bonded together by the mixed layer 14 in which both of the components are mixed together in a complex manner. For this reason, the bonding strength between the first layer 12 and the second layer 13 is sufficiently ensured without using an adhesive.

[0027] <Effects of the embodiment> According to the embodiment described above in detail, the following effects are achieved. (1) Laminate 11 includes a first layer 12 made of polypropylene and a second layer 13 made of thermosetting polyurethane laminated on first layer 12. First layer 12 and second layer 13 are joined by a mixed layer 14 in which both the polypropylene constituting first layer 12 and the thermosetting polyurethane constituting second layer 13 are mixed together.

[0028] According to the above configuration, the first layer 12 and the second layer 13 are bonded together by the mixed layer 14 in which both the polypropylene and the thermosetting polyurethane components constituting the first layer 12 and the second layer 13, respectively, are mixed together. That is, the first layer 12 and the second layer 13 are bonded together by the mixed layer 14 in which both the components are mixed together in a complex manner. This makes it possible to further increase the bonding strength between the first layer 12 and the second layer 13.

[0029] (2) The method for manufacturing the laminate 11 includes a first layer molding step of molding a first layer 12 made of polypropylene by injection molding, an amorphous layer forming step of forming an amorphous layer 19 on the surface of the first layer 12, a mold clamping step of clamping a second mold 21 in which the first layer 12 with the amorphous layer 19 formed on its surface is set, and a second layer molding step of injecting a thermosetting polyurethane precursor (first liquid and second liquid) into a second cavity 23 of the second mold 21, and hardening the precursor while allowing it to permeate the amorphous layer 19, thereby molding a second layer 13 made of thermosetting polyurethane.

[0030] According to the above method, the precursor of the thermosetting polyurethane hardens while permeating the amorphous layer 19 of the first layer 12 made of polypropylene, forming the second layer 13 made of thermosetting polyurethane. At this time, the amorphous layer 19 permeated with the precursor becomes a mixed layer 14 in which both the polypropylene and thermosetting polyurethane components constituting the first layer 12 and the second layer 13, respectively, are mixed in a complex manner. Therefore, the first layer 12 and the second layer 13 are integrally bonded in this mixed layer 14, and the bonding strength between the first layer 12 and the second layer 13 can be further increased.

[0031] (3) In the method for producing the laminate 11, the amorphous layer 19 formed in the amorphous layer forming step has a thickness of 5 nm or more and 500 nm or less. According to the above method, the thickness of the mixed layer 14 joining the first layer 12 and the second layer 13 is sufficiently ensured, so that the bonding strength between the first layer 12 and the second layer 13 can be more reliably increased. Incidentally, if the thickness of the amorphous layer 19 is less than 5 nm, it may be difficult to ensure a sufficient bonding strength between the first layer 12 and the second layer 13. On the other hand, if the thickness of the amorphous layer 19 exceeds 500 nm, there may be a wasted region in the amorphous layer 19 where the thermosetting polyurethane precursor (first liquid and second liquid) does not permeate in the second layer molding step.

[0032] <Example of change> The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other as long as they are not technically inconsistent.

[0033] The laminate 11 may be manufactured as follows. First, as shown in FIG. 11, in the first layer molding step, the first layer 12 is injection molded using the first mold 15 in the same manner as in the above embodiment. Then, the first mold 15 is opened. At this time, as shown in FIG. 12, the first layer 12 remains on the fixed mold 17 side. Then, in this state, in the amorphous layer forming step, the amorphous layer 19 is formed on the surface of the first layer 12 in the same manner as in the above embodiment. Then, as shown in FIG. 12 and FIG. 13, in the mold clamping step, the first layer 12 with the amorphous layer 19 formed on its surface is set in the second mold 21 obtained by replacing the first movable mold 18 with the second movable mold 22, and then the second mold 21 is clamped. Thereafter, in the second layer molding step, similarly to the above embodiment, the first liquid and the second liquid are mixed and injected into the space 25 in the second cavity 23 of the second mold 21 in which the first layer 12 has been set and closed, to mold the second layer 13. In this way, the laminate 11 is obtained.

[0034] The thickness of the amorphous layer 19 formed in the amorphous layer forming step does not necessarily have to be 5 nm or more and 500 nm or less. In the second layer molding process, in addition to the first liquid and the second liquid, various additives for the purpose of, for example, coloring may be mixed and injected into the space 25 in the second cavity 23 of the second molding die 21.

[0035] The first layer 12 may be made of a polyolefin other than polypropylene. That is, the first layer 12 may be made of, for example, polyethylene. The laminate 11 is not limited to exterior parts such as a vehicle bumper, but may also be embodied as interior parts of the vehicle, such as an instrument panel.

[0036] The laminate 11 may be applied to products other than vehicles. [Explanation of symbols]

[0037] 11...Laminate 12…1st layer 13…Second layer 14…Mixed layer 15...1st mold 16…First cavity 17…Fixed type 18...1st movable type 19...Amorphous layer 20…Corona discharge surface modification device 21... A second mold as an example of a mold 22…Second movable type 23…Second cavity 24…Cavity surface 25…Space A,B...components

Claims

1. A first layer made of polyolefin and a second layer made of thermosetting polyurethane laminated to the first layer, A laminate characterized in that the first layer and the second layer are joined by a mixed layer in which both components, a polyolefin constituting the first layer and a thermosetting polyurethane constituting the second layer, are mixed together.

2. a first layer molding step of molding a first layer made of polyolefin by injection molding; an amorphous layer forming step of forming an amorphous layer on a surface of the first layer; a mold clamping step of clamping a mold in which the first layer having the amorphous layer formed on the surface thereof is set; a second layer molding step of injecting a precursor of a thermosetting polyurethane into a cavity of the mold and curing the precursor while allowing the precursor to permeate the amorphous layer, thereby molding a second layer made of thermosetting polyurethane; A method for producing a laminate, comprising:

3. 3. The method for manufacturing a laminate according to claim 2, wherein the amorphous layer formed in the amorphous layer forming step has a thickness of 5 nm to 500 nm.

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