JP4762020B2 - Molding method and molded product - Google Patents

Description

  The present invention relates to a method of molding a molded article, and particularly used in exterior machines such as engine grills and machine cabs in work machines such as construction machines, agricultural machines, and forestry vehicles, and has an inner surface with irregularities such as ribs and bosses. The present invention relates to a method for forming a molded article having a coating film on both the surface and the outer surface.

  For example, a hydraulic excavator, which is one of construction machines, is provided with an upper swinging body that can swing freely above a lower traveling body. In addition to an operator cab, a boom, a counterweight, and the like, the upper swinging body includes an engine. An engine grill for storing the machine and a machine cab for storing hydraulic equipment and the like are disposed. These engine grills and machine cabs are generally large in size, and on the inner surface (rear surface), reinforcing ribs, bosses and the like are provided in an intricate shape. For this reason, exterior members such as engine grills and machine cabs are generally produced by molding synthetic resin by a reaction injection molding method (hereinafter simply referred to as RIM method).

  The RIM method is a molding method in which two or more types of low molecular weight and low viscosity raw materials are mixed using a mixing head, mixed and injected into the mold at the same time. Molding of molded products having large and complex shapes Suitable for In addition, since the molding pressure of the RIM method is lower than that of injection molding, it is possible to use a resin mold that is very inexpensive compared to a metal mold as a mold, and use a simple mold clamping device. It has the advantage that it can.

  In general, an exterior member of a work machine is coated on the outer surface (outer surface) of a molded body in order to improve the appearance quality and improve the appearance as a product. An example of a method for producing such a molded article having a coating on the outer surface by using the RIM method is disclosed in Japanese Patent Laid-Open No. 5-42561 (Patent Document 1) and Japanese Patent Laid-Open No. 8-72096 (Patent Document 2). ) Etc.

  For example, Patent Document 1 describes a method of manufacturing a decorative molded product that performs decoration simultaneously with molding in molding of a synthetic resin by the RIM method. Specifically, when molding by the RIM method, first, a decorative thermoplastic sheet softened by heating is interposed between a female mold having a vacuum suction hole and a sheet heating body, and the female mold and the thermoplastic sheet are interposed. The thermoplastic sheet is preliminarily formed into a shape that conforms to the shape of the cavity surface of the female mold by evacuating the space sealed by the above through a female vacuum suction hole. Next, after the female mold and the male mold are clamped, molding is performed by injecting a liquid material of synthetic resin into a cavity of a mold designed in a predetermined shape. Thereby, for example, when molding a molded product having a large and complicated shape, it is possible to obtain a molded product in which the decorative thermoplastic sheet is integrally attached to the surface.

  In addition, when molding a synthetic resin using the method described in Patent Document 1, a gas generated during molding moves upward, and a large number of voids are formed on the molding surface molded by the upper mold. It will be formed. For this reason, in recent years, for example, when a molded product in which a decorative sheet is integrally formed is manufactured, a preformed decorative sheet is generally arranged in a lower mold and molding is performed.

  As a result, for example, as shown in FIG. 4, in the molded body 21, the void 24 is formed in the portion where the rib 23 and the boss of the inner surface 22 formed by the upper mold are formed. No void is formed at the interface between the decorative sheet and the synthetic resin. For this reason, the adhesiveness of a synthetic resin and a decorating sheet is ensured, it can prevent that the decorating sheet peels, and the design property in an outer surface can be improved. In this case, the void 24 formed at the time of molding can be hidden behind the molded body 21 that cannot be seen from the outside when the molded body 21 is attached to the work machine.

  On the other hand, in Patent Document 2, when a coating film is formed on the surface of a molded product by an in-mold coat molding method during molding, it is possible to form a color-coded coating film on the surface of the RIM molded product. A multicolor in-mold coating method is described. In Patent Document 2, the in-mold coat molding method is a method in which a RIM raw material is filled in a cavity of a mold composed of an upper mold and a lower mold to mold a RIM molded product, and then the RIM molded product in the mold is molded. In this method, a coating is formed on the surface of the RIM molded product by injecting a coating material into the gap between the surface of the RIM molded product and the upper mold cavity surface caused by the shrinkage from the coating injection hole of the upper mold.

  In the molding method in Patent Document 2, when a coating film is formed on the surface of a RIM molded product by an in-mold coating molding method, a partitioning convex portion for partitioning the gap into a plurality of sections is provided on the cavity surface on the coating film forming side. In addition, a paint injection hole is provided on each cavity surface, and after the RIM molded product contracts in the mold, each partition of the gap partitioned by the partitioning convex portion has a predetermined color. It is characterized by injecting paint from each paint injection hole. According to such a molding method, since a paint having a predetermined color can be injected into each section partitioned by the partitioning convex portion, the paint does not mix between the sections, and is applied to the surface of the RIM molded product. A beautifully color-coded coating film can be formed.

  On the other hand, other methods for applying the coating to the outer surface of the molded body include, for example, post-coating in which a predetermined region is applied after molding a molded product, or pre-coating the mold cavity surface before molding. In addition, there is known a technique such as in-mold coating for producing a molded product in which a coating film is molded and integrated on the outer surface by transferring the paint to a molded product at the time of molding. In the post-coating, for example, a coating film is formed by performing processes such as sanding, primer coating, finish coating, baking, etc. on the molded product, but there is a problem that it takes a lot of work steps and takes time. On the other hand, in-mold coating has the advantage that the number of steps can be reduced and the cost can be kept low because the coating can be applied to the cavity surface of the mold by spraying before molding.

  By the way, engine grills and machine cabs of work machines are required to have a certain degree of rigidity and strength in order to protect the engine and the like, and for example, weight reduction is required so that opening and closing can be easily performed during maintenance. . On the other hand, polyurethane, which is one of synthetic resins, can be molded by the RIM method and has excellent moldability. Further, by using hard polyurethane as a molding material, a molded product having a light weight, high rigidity, and excellent weather resistance can be reasonably obtained. Furthermore, in the molding of polyurethane, since it is possible to give a texture pattern to the surface of the molded body, there is an advantage that a beautiful and high-quality molded product can be obtained.

  Therefore, at present, hard polyurethane is often used as a molding material in molded products used for engine grills and machine cabs of work machines, and the outer surface of a molded body made of such hard polyurethane is coated. Even in this case, the above-described coating method is used.

In addition, work machines such as hydraulic excavators and wheel loaders have a problem that noise generated from an engine, hydraulic equipment, or the like is large during operation. Therefore, conventionally, in order to reduce noise generated from an engine, hydraulic equipment, etc., means such as affixing a sound absorbing material to the inner surface of the engine grill or the machine cab for storing them have been taken. Such a sound-absorbing material is formed so as not to interfere with ribs, bosses and the like formed on the inner surface of the molded body after molding the molded body whose outer surface is coated by the RIM method as described above, for example. Cut into a predetermined shape and pasted.
Japanese Patent Laid-Open No. 5-42561 Japanese Patent Laid-Open No. 8-72096

  In general, in a working machine such as a hydraulic excavator or a wheel loader, for example, when maintenance is performed on an engine or a hydraulic device, an exterior member such as an engine grill or a machine cab is opened for inspection or maintenance. At that time, the engine grill and the inner surface of the machine cab, which are normally invisible from the outside, are visible to the human eye, and in recent years, it is desired to improve the appearance quality of the inner surface of the exterior member.

  However, on the inner surface of the molded body molded by the RIM method as described above, for example, voids are easily formed at the sites where the ribs and bosses are formed as described above, and for example, a sound absorbing material is pasted on the inner surface. Even in these cases, these portions are exposed without the sound absorbing material being pasted, which causes a deterioration in appearance quality. Therefore, in order to improve the appearance quality of the inner surface of the engine grill and the machine cab, it has been demanded to uniformly coat not only the outer surface but also the entire inner surface.

  However, for example, when molding is performed by the method described in Patent Document 1, voids are formed on the inner surface of the molded body molded by the upper mold as described above. For this reason, in order to improve the quality of the inner surface, the voids formed on the inner surface must be manually repaired and then post-painted, which complicates the operation and increases the cost burden. There was a problem.

  Further, for example, when molding is performed using an inexpensive resin mold as a mold, a mold release agent having a lower melting point than that of a mold is used as a mold release agent applied to the resin mold at the time of molding. For this reason, when the molded product is taken out from the resin mold after molding, a release agent is adhered to the surface of the molded product together. Accordingly, when post-coating as described above is performed, in order to improve the adhesion of the coating film, it is necessary to perform a sandblasting treatment on the molded product before coating to remove the release agent from the molded product. However, since the inner surface of the molded product has a complicated surface shape with ribs and bosses formed, a large number of steps are required for removal of the release agent and subsequent coating, which is also complicated. become.

  Moreover, as a method of forming a coating film on the outer surface and the inner surface of the molded product, for example, as shown schematically in FIGS. 5 (a) and 5 (b), the decorative sheet is attached to the lower mold 32 during molding. 33 is applied to form a coating film on the outer surface of the molded product 34, and the coating 35 is previously applied to the cavity surface of the upper mold 31 by using the above-mentioned in-mold coating on the inner surface of the molded product 34. It is conceivable that the coating film 35 ′ is formed by keeping the film.

  However, in this case as well, the gas generated during molding is accumulated on the inner surface of the molded product 34 (particularly at the ribs and bosses) during molding, and voids 36 are formed. For this reason, there is a problem in that the coating 35 cannot be transferred at the site of the molded product 34 where the void 36 is formed, and the coating film 35 ′ cannot be stably formed. Further, when the paint 35 cannot be transferred to the molded product 34, the paint 35 remains in the upper mold 31. For this reason, the operation | work which cleans the upper mold | type 31 after shaping | molding and removes the remaining coating material 35 is required, and it becomes one of the factors which raises a cost.

  In addition, as another method of forming a coating film on the outer surface and inner surface of the molded body, it is possible to arrange the decorative sheet not only in the lower mold but also in the upper mold before molding, in this case, There is a drawback that it is difficult to preform the decorative sheet in accordance with the surface shape of the inner surface on which ribs, bosses and the like are formed. Moreover, since a void is formed at the interface between the decorative sheet arranged on the upper mold and the synthetic resin, there arises a problem that the adhesiveness between the two is lowered.

  On the other hand, in the case of forming a coating film on the surface of a molded product by injecting a paint into a gap formed between the molded product and a mold after molding the molded product as in Patent Document 2, A coating film can be formed only on either one of the outer surface or the inner surface. For this reason, the other surface must be separately coated thereafter to form a coating film, which increases the number of steps and leads to an increase in cost. Furthermore, in order to form a coating film by the in-mold coating method of Patent Document 2, it is necessary to pour the paint with a very high pressure into the gap formed between the molded product and the mold. However, there is a problem that a mold that can sufficiently withstand high pressure has to be manufactured, and the burden on the cost becomes very large.

  The present invention has been made in view of the above-described conventional problems, and its specific purpose is to prevent the generation of voids during molding, and both the outer surface and the inner surface having irregularities such as ribs and bosses. To provide a molding method capable of easily and inexpensively molding a molded product having a coating film on its surface, and to easily apply a sound absorbing material to the inner surface having the coating film The object is to provide a molding method capable of achieving the above.

In order to achieve the above object, the molded product molding method provided by the present invention is used as an exterior member such as an engine grill of a work machine as a basic configuration, and has an inner surface having irregularities such as ribs and bosses. A method for forming a molded article having a coating film on a first surface that is a surface and a second surface that is an outer surface, the upper die having a cavity surface capable of forming the first surface; Producing a lower mold having a cavity surface capable of forming the second surface, applying a paint to the cavity surface of the upper mold, and clamping the lower mold and the upper mold coated with the paint. , Polyol, polyamine, and water are mixed , and the ratio of the urethane reaction and the urea reaction of the urethane urea resin is such that the ratio of the components is urethane reaction: urea reaction = (3-5) :( 7-5) adjust by first mixing raw materials preparation child The polyisocyanate is mixed with the first mixed raw material to prepare a second mixed raw material, and at the same time, the second mixed raw material is injected into a cavity formed between the upper mold and the lower mold to react. The main feature is that it includes foaming a molded product made of urethane urea resin by an injection molding method and transferring the paint to the molded product.

  In the molding method of the present invention, in order to form the coating film on the second surface, the lower die and the upper die are pre-shaped into a predetermined shape on the cavity surface before clamping the lower die and the upper die. It is possible to arrange a decorative sheet. In this case, it is preferable to use the decorative sheet made of a combination of any one or two or more selected from vinyl chloride resin, methacrylic resin, ABS resin, AES resin, and urethane resin. .

In the molding method of the present invention, in order to form the coating film on the second surface, a paint is applied to the cavity surface of the lower die before clamping the lower die and the upper die. Is possible. In this case, it is preferable to use an aliphatic polyurethane resin paint as a paint applied to the cavity surface of the lower mold.
Furthermore, in order to form the coating film on the second surface, after the reaction injection molding is performed, the second surface side of the obtained molded product may be coated.

In the present invention, it is preferable to use an aliphatic polyurethane resin paint as the paint applied to the cavity surface of the upper mold.
Moreover, it is preferable that the shaping | molding method which concerns on this invention sticks a sound-absorbing material to the said 1st surface side of the obtained molded article after the said reaction injection molding. In this case, it is preferable to apply a release agent having a melting point higher than that of the urethane urea resin to the cavity surface of the upper mold before applying the paint, and as the upper mold and the lower mold, zinc is used. It is preferable to use an alloy mold.

  Next, in the present invention, a molded product molded by the molding method having the above-described configuration is provided. In this case, the average diameter of the bubbles formed in the molded product is 10 μm or more and 40 μm or less, and the diameter of each bubble formed in the molded product is 4 μm or more and 100 μm or less.

  In the molding method according to the present invention, after forming an upper mold capable of molding a first surface having irregularities as a mold and a lower mold capable of molding the second surface, and applying a paint to the cavity surface of the upper mold Clamp the same mold and lower mold. Then, a mixed raw material of urethane urea resin is injected into the cavity between the upper mold and the lower mold, a molded product made of urethane urea resin is foam-molded by the RIM method, and the paint is transferred to the first surface of the molded product. To form a coating film.

  The inventor can simply and rationally paint the inner surface when forming a molded article having coatings on both the inner surface (first surface) and the outer surface (second surface) having irregularities. We conducted extensive experiments and studies. As a result, it has been found that voids are not formed on the first surface of a molded product molded by the upper mold by using a urethane urea resin that has not been used conventionally as a material of a molded body that becomes an exterior member. It was.

  The factor that prevents the formation of such voids is not yet clear, but it is probably because the following process occurs in the molding of urethane urea resin by the RIM method. That is, gas is generated in the urethane reaction at the time of molding, but no gas is generated in the urea reaction. Therefore, the gas generated by the urethane reaction is taken into the urea component until the urethane urea resin is cured, so that the gas is As a result of dispersing in the entire molded product without concentrating on the skin layer formed in the vicinity of the upper mold, bubbles are formed in the urethane urea resin, and void formation is prevented on the first surface of the molded product. It is done.

  And when the present inventors prevented the formation of voids on the first surface of the molded product as described above at the time of molding, the coating of the first surface on the upper mold side was conventionally stabilized by the formation of voids. We thought that it would be possible to perform by in-mold coating, which was difficult to paint, and completed the present invention.

  That is, according to the molding method of the present invention, urethane urea resin is adopted as a molding material, and the first surface of a molded product having projections and depressions is applied by in-mold coating, thereby suppressing generation of voids during molding. A molded product having a uniform coating film on the first surface molded by the upper mold and the second surface molded by the lower mold can be molded easily and at low cost. In addition, the urethane urea resin as used in the field of this invention means the single synthetic resin which has a urethane bond and a urea bond.

  In the molding method of the present invention, when the mixed material of the urethane urea resin is prepared, the ratio of the urethane reaction and the urea reaction is urethane reaction: urea reaction = (3-5) :( 7-5). The component ratio of the mixed material of urethane urea resin is adjusted. Thereby, the suitable hardening time of urethane urea resin can be ensured, and the molded article which has suitable intensity | strength as an exterior member of a working machine can be shape | molded stably.

  In the molding method of the present invention, the method for forming the coating film on the second surface is not particularly limited. For example, before the lower mold and the upper mold are clamped, the decorative sheet pre-shaped into a predetermined shape is By disposing on the cavity surface of the mold, the coating film can be easily and stably formed on the second surface of the molded product.

  In this case, as the decorative sheet, a sheet made of a combination of any one or two or more selected from vinyl chloride resin, methacrylic resin, ABS resin, AES resin, and urethane resin is used. it can. Thereby, the coating film which has the outstanding weather resistance and glossiness can be formed in the 2nd surface side of a molded article, and the external appearance quality of the 2nd surface of a molded article can be improved.

  Further, as a method of forming a coating film on the second surface, in-mold coating in which a paint is applied to the cavity surface of the lower mold before the lower mold and the upper mold are clamped can be used. If the second surface is thus coated by in-mold coating, a uniform coating can be easily formed on the second surface at low cost. In this case, a coating film excellent in weather resistance can be formed on the second surface of the molded product by using an aliphatic polyurethane resin coating as a coating applied to the cavity surface of the lower mold. In addition, it is possible to impart a texture to the surface of the coating film, or to add various colors to the coating film by adding a pigment or the like to the aliphatic polyurethane resin paint.

  Further, as another method for forming a coating film on the second surface, post-coating may be used in which the second surface of the obtained molded product is coated after the reaction injection molding. Thereby, a uniform coating film can be stably formed on the second surface of the molded product.

  In the molding method of the present invention, a coating film excellent in weather resistance can be formed on the first surface of the molded product by using an aliphatic polyurethane resin coating as the coating applied to the cavity surface of the upper mold. it can. In addition, it is possible to impart a texture to the surface of the coating film, or to add various colors to the coating film by adding a pigment or the like to the aliphatic polyurethane resin paint.

  Furthermore, in the molding method of the present invention, after the reaction injection molding, a sound absorbing material can be attached to the first surface side of the obtained molded product. Thereby, when the manufactured molded article is applied as an engine grill or a machine cab of a work machine, an excellent soundproofing effect can be exhibited.

  In addition, when a sound absorbing material is applied to the first surface side of the molded product as described above, before applying the paint to the cavity surface of the upper mold, a separation having a higher melting point than the urethane urea resin is applied to the cavity surface of the upper mold. A mold is applied.

  For example, when the melting point of the release agent applied to the cavity surface of the molding die is lower than the melting point of the molding material, the release agent adheres to the molded product side when the molded product is taken out from the mold after molding. In this case, when a sound absorbing material is affixed to the surface of the obtained molded product, it is necessary to remove the mold release agent on the surface of the molded product in order to ensure the adhesive force of the sound absorbing material. However, by using a mold release agent having a melting point higher than that of the molding material as in the present invention, when the molded product is taken out from the mold, the mold release agent does not adhere to the surface of the molded product. It can be left on the cavity surface. Therefore, when the sound absorbing material is subsequently attached to the surface of the molded product, the step of removing the release agent is not necessary, and the attaching operation can be simplified.

  Furthermore, in this case, by using a zinc alloy mold (hereinafter abbreviated as ZAS mold) as the upper mold and the lower mold, the melting point is higher than that when a resin mold is used as a release agent applied to the cavity surface. A high mold release agent can be used. For this reason, it can prevent more reliably that a mold release agent adheres to the surface of a molded article.

  And the molded product shape | molded by the shaping | molding method of this invention provided with the said structure is a uniform coating film on the 1st surface used as the inner surface which has unevenness | corrugations, such as a rib and a boss | hub, and the 2nd surface used as an outer surface. It becomes a cheaper molded product than the conventional one provided with.

  In the molded product of the present invention, the average diameter of the bubbles formed in the urethane urea resin is 10 μm or more and 40 μm or less, and the diameter of each bubble is 4 μm or more and 100 μm or less. If it is a molded product made of urethane urea resin in which bubbles of such size are formed, there is no sink (recess) on the back side of the part where ribs and bosses are formed, and it is lightweight with excellent strength It becomes a molded product. For this reason, it can be used very suitably as an engine grill or machine cab of a working machine.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  FIG. 1 is an explanatory view schematically illustrating the steps of the molding method according to Example 1 of the present invention. In FIG. 1, in order to facilitate understanding of the features of the present invention, the shape, dimensions, and the like are shown differently from the actual ones. In the following, a method for forming a molded product having a coating film on both sides of the first surface having ribs and having irregularities and the second surface on the opposite side is described. The case where the formation of the coating film on the second surface is performed by molding and integrating the decorative sheet is described as an example. However, the present invention is not limited to this, and various modifications are possible as long as they have the above basic configuration and can solve the problems of the present invention. For example, a resin mold can be used as the mold instead of the ZAS mold, and the coating on the second surface can be formed using in-mold coating, post-coating, or other coating methods. It is.

  First, in the molding method according to the first embodiment, as shown in FIG. 1A, the upper mold 2 having a cavity surface capable of molding the first surface of the molded product 10 and the second surface can be molded. A ZAS mold 1 including a lower mold 3 having a cavity surface is prepared and prepared. In the first embodiment, the cavity surfaces of the upper mold 2 and the lower mold 3 are predetermined so that a molded product 10 having a plurality of ribs 11 on the first surface and having a flange 12 on the peripheral edge can be formed. It is formed in the shape of.

  Further, the upper die 2 is provided with a mixing head 13 for preparing a raw material of urethane urea resin as a molding material, and a mixed raw material of urethane urea resin prepared by the mixing head 13 is directly injected into the cavity 8. It is configured as follows. In particular, in Example 1, since a urethane urea resin having a short curing time after mixing the raw materials is used as a molding material, a substantially central portion of the upper mold 2 is formed so that the raw materials can be quickly filled into the cavity 8. A mixing head 13 is arranged.

  Further, the upper mold 2 is formed with a vent groove 5 for discharging the gas existing in the cavity 8 when the mixed raw material is injected into the cavity 8. An ejector pin 4 is provided for projecting 10 and smoothly removing the same. The vent groove 5 is provided at a position along the parting line at the downstream end when the mixed raw material flows into the cavity 8. In addition, the upper mold | type 2 and the lower mold | type 3 which have such a shape can be easily produced with the method used conventionally. In the first embodiment, the upper mold 2 can be configured so that gas can be extracted from the gaps of the ejector pins 4 as necessary.

  After the upper mold 2 and the lower mold 3 having a predetermined shape as described above are produced, a release agent is applied to each cavity surface. In Example 1, since the mold is made of a zinc alloy, a release agent having a melting point higher than that of the urethane urea resin can be used.

  Next, as shown in FIG. 1B, in order to form a coating film on the first surface of the molded product 10 by in-mold coating at the time of molding, the coating 6 is applied to the cavity surface of the upper mold 2 produced above. Apply by spraying. At this time, by using an aliphatic polyurethane resin paint as the paint 6, it is possible to form a coating film having excellent weather resistance on the first surface of the molded product. Moreover, it becomes possible to give various colors to a coating film by making an aliphatic polyurethane resin paint contain a pigment or the like.

  Further, in order to apply the paint 6 to the cavity surface of the upper mold 2 and to form a coating film on the second surface of the molded product 10, the lower mold 3 is preshaped so as to follow the shape of the cavity surface. The decorated decoration sheet 7 is set. The decorating sheet 7 has been subjected to predetermined decorating in advance. In addition, the method of pre-shaped the decorating sheet 7 is not specifically limited, The method generally performed conventionally can be used.

  For example, a vacuum suction hole (not shown) is provided in the lower mold 3, and a suction pump (not shown) or the like is connected to the vacuum suction hole, and the thermoplastic decorative sheet 7 softened by heating is lowered. Place on mold 3. Thereafter, the softened decorative sheet 7 is sucked into close contact with the lower mold 3 and cooled by being sucked through a vacuum suction hole with a suction pump or the like. Thereby, the decorative sheet 7 can be set in the lower mold 3 in a state of being shaped into a shape along the cavity surface of the lower mold 3.

  The material of the decorative sheet 7 set in the lower mold 3 is not particularly limited. For example, any one or two selected from vinyl chloride resin, methacrylic resin, ABS resin, AES resin, and urethane resin are used. A decorative sheet made of a combination of the above can be used. Thereby, the coating film which has the outstanding weather resistance and glossiness can be formed in the 2nd surface of the molded article 10, and the quality of the molded article 10 can be improved. In addition, the decorative sheet 7 can be subjected to treatments such as coloring, various pattern printing, metal deposition, and the like, whereby various designs can be imparted to the second surface of the molded product 10.

  As described above, the aliphatic polyurethane resin paint 6 is applied to the cavity surface of the upper mold 2, and after the decorative sheet 7 is set on the lower mold 3, the upper mold 2 and the lower mold 3 are clamped (see FIG. 1 (c)). Thereby, a cavity 8 having a predetermined shape is formed between the upper mold 2 and the lower mold 3.

  Thereafter, a raw material of urethane urea resin as a molding material is prepared by the mixing head 13. In preparing the raw material, first, a first mixed raw material is prepared by mixing a polyol, a polyamine, and water in a predetermined amount. At this time, if necessary, a foam stabilizer, a catalyst, a colorant, nitrogen gas, and the like can be appropriately mixed in the first mixed raw material.

  Next, the produced first mixed raw material and a predetermined amount of polyisocyanate are introduced into the mixing head 13 and mixed to prepare a second mixed raw material 9. At this time, since the polymerization reaction and curing of the urethane urea resin starts by mixing the first mixed raw material and the polyisocyanate, the second mixed raw material 9 is prepared from the mixing head 13 at the same time as the second mixed raw material 9 is prepared. It inject | pours into the cavity 8 of the metal mold | die 1 at high speed ((d) of FIG. 1).

  Moreover, when preparing the 2nd mixing raw material 9, in the reaction of urethane urea resin, the ratio of urethane reaction and urea reaction will be urethane reaction: urea reaction = (3-5) :( 7-5). In addition, the component ratio of the mixed raw material is preferably adjusted so that urethane reaction: urea reaction = 4: 6.

  At this time, if the ratio of the urea reaction exceeds 70%, the curing time of the urethane urea resin becomes too short. Therefore, when molding a large molded product used for an exterior member of a work machine, In addition, the second mixed raw material 9 cannot be sufficiently filled, and it may be difficult to obtain a molded product having a predetermined shape. Moreover, when the ratio of the urea reaction becomes too large, the bending strength and bending elastic modulus of the obtained molded product are lowered, and the strength and rigidity required for the exterior member of the work machine may not be obtained.

  On the other hand, when the ratio of the urea reaction is less than 50%, there is a risk that problems such as a decrease in the high-temperature strength of the molded product may occur. In Example 1, the second mixed raw material 9 was prepared so as to be urethane reaction: urea reaction = 4: 6 and injected into the cavity 8 of the ZAS mold 1 at high speed. In this case, the curing time of the urethane urea resin after mixing the polyisocyanate is about 5 seconds.

  Here, as a polyol, polyether polyol, polyester polyol, polycarbonate polyol, polycaprolactone polyol, epoxy polyol, acrylic polyol etc. can be used, for example. Examples of polyamines that can be used include modified aliphatic polyamines, modified alicyclic polyamines, modified aromatic polyamines, aliphatic polyamines, alicyclic polyamines, and aromatic polyamines. Furthermore, as a polyisocyanate, aliphatic polyisocyanate, alicyclic polyisocyanate, aromatic polyisocyanate, etc. can be used, for example.

  Then, the second mixed raw material 9 is caused to flow from the mixing head 13 toward the end of the cavity 8 to fill the cavity 8 with the second mixed raw material 9, and the urethane urea resin is reacted in the cavity 8 to be cured. Thereby, the molded article 10 made of urethane urea resin is molded ((e) of FIG. 1). At this time, gas is generated in the urethane reaction, but the generated gas is taken into the urea component until the urethane urea resin is cured, thereby forming fine bubbles in the entire molded product, and the molded product. It is considered that the formation of voids as in the prior art can be prevented on the first surface side.

  Therefore, if RIM molding of urethane urea resin is performed as described above, voids are not formed on the first surface of the molded product 10, and therefore, even if in-mold coating is performed on the first surface, it is shown in FIG. 5 described above. Such a coating failure does not occur, and the coating film 6 'can be stably formed on the first surface. Further, the ZAS type cleaning performed thereafter is also facilitated.

  Further, the urethane urea resin is slightly foamed simultaneously with the polymerization reaction. For example, when a non-foamed type synthetic resin (for example, polyurethane) is molded by the RIM method, there is a problem that sink marks occur on the back side of the part where the ribs and bosses of the molded product are formed. The generation of sink marks can be prevented by the fine foaming of the urethane urea resin during molding, and the molded product 10 having a predetermined shape can be stably formed.

  When the urethane urea resin is cured in the mold 1, the mold is opened and the molded product 10 is ejected by the ejector pins 4, so that a rib is formed on the first surface serving as the inner surface, and an aliphatic polyurethane resin paint is used. The formed article 10 having excellent appearance quality can be obtained in which the formed coating film 6 ′ is provided and the decorative sheet 7 is molded and integrated on the second surface serving as the outer surface.

  That is, when a coating film is conventionally formed on the first surface serving as the inner surface having irregularities and the second surface serving as the outer surface, in order to stably form a uniform coating film on the first surface, In contrast to the fact that after the molding, the void must be repaired and post-coating had to be carried out, whereas with the method of the first embodiment as described above, void repairing work was not necessary and the number of processes was more than post-coating. A uniform coating film can be stably formed on the first surface by simple and in-mold coating. For this reason, compared with the conventional method, the simplification and cost reduction of a work process can be achieved, and a low-cost molded product can be provided.

In addition, the molded product 10 obtained as described above has a density of 0.4 g / cm ³ or more and 1.0 g / cm ³ or less, and bubbles are formed therein. In Example 1, the average diameter of the bubbles formed in the molded product 10 is 10 μm or more and 40 μm or less, and the diameter of each bubble is 4 μm or more and 100 μm or less. The molded product 10 having such density and cell size is lighter than, for example, a non-foamed polyurethane molded product, and has sufficient strength as an exterior member.

  Further, when the molded product 10 obtained in Example 1 is used as an exterior member, a sound absorbing material can be attached to the first surface of the molded product 10 in order to enhance the soundproofing effect. The area of the sound absorbing material in the molded article 10 is not particularly limited, but for example, it is preferable to apply the sound absorbing material to an area excluding the rib. For example, after the sound absorbing material is cut in accordance with the shape of the attaching area, the sound absorbing material Is attached to the molded product using an adhesive or the like. Note that the sound absorbing material can be the same as the conventional one, and for example, a sound absorbing material made of polyurethane foam, polyethylene foam or the like is preferably used.

  At this time, in Example 1, since a mold having a high melting point is used as a mold release agent at the time of molding as described above, the mold release agent is left in the mold 1 when the molded product is taken out from the mold. Thus, adhesion to the molded product 10 can be prevented. Therefore, when a sound absorbing material is affixed to the molded product 10, it is not necessary to remove the release agent from the molded product 10, and the sound absorbing material can be easily affixed. Since the molded product thus manufactured has an excellent soundproofing effect, it can be very suitably applied as an engine grill or a machine cab of a work machine.

  In Example 1, the coating film formed on the second surface of the molded product 10 is formed by molding and integrating the decorative sheet 7 with the molded product 10. Is not limited to this. For example, the coating film formed on the second surface of the molded product can be formed by in-mold coating in the same manner as the coating film formed on the first surface. Thus, when performing in-mold coating on the second surface, a coating film can be formed by applying paint to the cavity surface of the lower mold by spraying or the like without preparing a decorative sheet or pre-shaped. Therefore, a molded product can be obtained more easily in a short time. The coating applied to the cavity surface of the lower mold is not particularly limited. For example, an aliphatic polyurethane resin coating is used on the second surface in the same manner as the coating formed on the first surface. Can be formed.

  In addition, at the time of molding, it is also possible to form a coating film only on the first surface of the molded product by in-mold coating, and then separately coat only the second surface to form the coating film. In the present invention, since it is possible to prevent the occurrence of sink marks on the molded product as described above, even when a coating film is formed on the second surface by post-coating, coating is performed without performing repair or the like on the second surface after molding. It becomes possible to carry out simply.

  Next, the molding method according to Example 2 of the present invention will be described. Here, FIG. 2 is an explanatory diagram schematically illustrating the steps of the molding method according to Example 2, and FIG. It is arrow sectional drawing of the III-III line shown to 2 (a). In FIG. 3, the shape of the upper cavity surface and the ejector pins are not shown in order to facilitate understanding of the arrangement positions of the mixing head, sprue, and vent groove. In the second embodiment, members having the same configuration as the members described in the first embodiment are denoted by the same reference numerals. About the member represented with the same code | symbol, since it is the same as that of the said Example 1, the description is abbreviate | omitted.

  In the molding method according to the second embodiment, as shown in FIG. 2A, the upper mold 2 ′ having a cavity surface capable of molding the first surface of the molded product 10 and the second surface can be molded. A ZAS mold 1 ′ composed of a lower mold 3 ′ having a cavity surface is prepared and prepared. In the upper mold 2 ′ and the lower mold 3 ′ used in the second embodiment, a sprue 14, a runner 15 and a gate 16 for injecting a mixed raw material of urethane urea resin into the cavity 8 are provided along the parting line. In addition, the nozzle of the mixing head 13 is connected to the sprue 14.

  As shown in FIG. 3, the sprue 14 is formed so that the dimension in the width direction gradually increases toward the runner 15, and the runner 15 and the gate 16 extend over the entire length in the width direction of the cavity 8. It is formed linearly across. In addition, since the urethane urea resin has a short curing time after mixing raw materials as described above, the positions where the sprue 14, the runner 15 and the gate 16 are formed are very important. It is determined in consideration of the shape of the cavity 8 and the flow distance of the mixed raw material.

  Further, the upper mold 2 is provided with a vent groove 5 for discharging gas and an ejector pin 4 for smoothly taking out the molded product 10. The vent groove 5 is formed at a position along the parting line on the downstream side (the end opposite to the gate 16) when the mixed raw material injected from the gate 16 flows into the cavity 8.

  After the upper mold 2 'and the lower mold 3' having the predetermined shapes as described above are manufactured, a release agent is applied to each cavity surface. Next, as shown in FIG. 2 (b), paint 6 is applied to the cavity surface of the upper mold 2 by spraying, and a pre-shaped decorative sheet 7 is set on the cavity surface of the lower mold 3, Thereafter, the upper mold 2 and the lower mold 3 are clamped ((c) in FIG. 2). Thereby, a cavity 8 having a predetermined shape is formed between the upper mold 2 and the lower mold 3.

  Thereafter, the second mixed raw material 9 of urethane urea resin, which is a molding material, is prepared by the mixing head 13, and at the same time, the second mixed raw material 9 is formed from the mixing head 13 through the sprue 14, runner 15, and gate 16. It is injected into the cavity 1 'at high speed ((d) in FIG. 2). At this time, the second mixed raw material 9 injected from the gate 16 is filled into the cavity 8 from the gate 16 side toward the opposite end, and the urethane urea resin is reacted in the cavity 8. Harden. Thereby, the molded article 10 made of urethane urea resin is molded ((e) of FIG. 2).

  And after urethane urea resin hardens | cures in metal mold | die 1 ', it has a rib in the 1st surface used as an inner surface by opening a mold | die and projecting the molded article 10 with the ejector pin 4, and an aliphatic. It is possible to obtain a molded article 10 having excellent appearance quality, which is provided with a coating film 6 ′ formed of a polyurethane resin paint and in which the decorative sheet 7 is molded and integrated on the second surface which is the outer surface. . By performing RIM molding of the urethane urea resin according to Example 2 as described above, the same effects as those of Example 1 can be obtained.

  INDUSTRIAL APPLICABILITY The present invention can be effectively applied when molding a molded product used as an engine grill, a machine cab, or the like in a work machine such as a construction machine, an agricultural machine, or a forestry vehicle.

(A)-(e) is explanatory drawing which illustrates typically the shaping | molding method which concerns on Example 1 of this invention. (A)-(e) is explanatory drawing which illustrates typically the shaping | molding method which concerns on Example 2 of this invention. It is arrow sectional drawing of the III-III line | wire shown to Fig.2 (a). It is a schematic diagram which shows typically a part of inner surface of the molded object used as an engine grill. It is explanatory drawing which illustrates typically the coating defect which generate | occur | produces when the surface of the upper mold | type side is painted by the in-mold coating in the conventional shaping | molding method.

Explanation of symbols

1,1 'mold (ZAS type)
2, 2 'Upper mold 3, 3' Lower mold 4 Ejector pin 5 Vent groove 6 Paint 6 'Paint film 7 Decorating sheet 8 Cavity 9 Second mixed raw material 10 Molded product 13 Mixing head 14 Sprue 15 Runner 16 Gate 21 Molded body 22 Inner surface 23 Rib 24 Void 31 Upper mold 32 Lower mold 33 Decorative sheet 34 Molded product 35 Paint 35 'Paint film 36 Void

Claims (13)

Molded product (10) used as an exterior member for engine grills, etc. of work machines, and having a coating film on a first surface serving as an inner surface having irregularities such as ribs and bosses, and a second surface serving as an outer surface A method of molding
Producing an upper die (2, 2 ') having a cavity surface capable of forming the first surface and a lower die (3, 3') having a cavity surface capable of forming the second surface;
Applying paint (6) to the cavity surface of the upper mold (2, 2 ');
Clamping the lower mold (3, 3 ') and the upper mold (2, 2') coated with the paint (6);
Polyol, polyamine, and water are mixed , and the ratio of the urethane reaction and the urea reaction of the urethane urea resin is adjusted so that the ratio of the components is urethane reaction: urea reaction = (3-5) :( 7-5). Adjusting to prepare the first mixed raw material,
The second mixed raw material (9) is prepared by mixing the first mixed raw material with polyisocyanate, and at the same time, the second mixed raw material (9) is mixed with the upper mold (2,2 ') and the lower mold (3,3). ') Is injected into the cavity (8) formed between the two and foamed molding (10) made of urethane urea resin by a reaction injection molding method, and the paint (6) is molded into the molded product (10). To transcribe to,
A molding method comprising: In order to form the coating film on the second surface,
A decorative sheet pre-shaped into a predetermined shape on the cavity surface of the lower mold (3, 3 ') before clamping the lower mold (3, 3') and the upper mold (2, 2 ') molding method according to claim 1, characterized in that it comprises a placing (7). The decorative sheet (7) is made of a combination of any one or more selected from vinyl chloride resin, methacrylic resin, ABS resin, AES resin, and urethane resin. The molding method according to claim 2 . In order to form the coating film on the second surface,
Before the lower mold (3, 3 ') and the upper mold (2, 2') are clamped, comprising applying a paint to the cavity surface of the lower mold (3, 3 ') The molding method according to claim 1 . The molding method according to claim 4 , wherein an aliphatic polyurethane resin paint is used as a paint applied to the cavity surface of the lower mold (3, 3 '). In order to form the coating film on the second surface,
Wherein after the reaction injection molding, the resulting molded method according to claim 1, characterized in that it comprises that the coating applied to the second surface of the molded article (10). The molding method according to any one of claims 1 to 6 , wherein an aliphatic polyurethane resin paint is used as the paint (6) applied to the cavity surface of the upper mold (2, 2 '). The molding method according to any one of claims 1 to 7 , wherein after the reaction injection molding, a sound absorbing material is attached to the first surface side of the obtained molded product (10). Claim 1-8, characterized in that the the cavity surface of the paint the upper mold before applying a (6) (2,2 ') is coated with a release agent having a melting point higher than the urethane urea resin The molding method according to any one of the above. The molding method according to any one of claims 1 to 9 , wherein a die made of a zinc alloy is used as the upper mold (2, 2 ') and the lower mold (3, 3'). Molded article characterized by being molded by a molding method according to any one of claims 1-10. The molded product according to claim 11, wherein the average diameter of the bubbles formed in the molded product is 10 µm or more and 40 µm or less. The molded product according to claim 11 or 12, wherein the diameter of each bubble formed in the molded product is 4 µm or more and 100 µm or less.

Images