JP2009052857A - Cooling device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cooling device having an improved appearance condition and reduced cost with a reduction of the usage amount of a hard polyurethane foam by using the hard polyurethane foam containing a reinforcing material different from the hard polyurethane foam for improving the resin strength of the foam or quickening the cooling of the foam to suppress the deformation of the foam. <P>SOLUTION: The hard polyurethane foam contains the other reinforcing material than the hard polyurethane foam. The reinforcing material is formed of an organic and/or inorganic material in needle, plate or spherical shape. It accounts for 20-40 wt.% of the total weight of the urethane foam including foaming agent and auxiliary agent, and has a length of 300 μm or smaller and a sectional major length of 20 μm or smaller. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a cooling device, and is particularly suitable for a heat insulating box and a heat insulating door of a cooling device such as a refrigerator, a freezer, a refrigerated showcase, and a vending machine filled with rigid polyurethane foam.

  Conventionally, a heat insulating material filled with a rigid polyurethane foam having closed cells in the space between an outer box and an inner box has been used for a heat insulating box body of a refrigerator. This rigid polyurethane foam is obtained by reacting a polyol component and an isocyanate component in the presence of a foaming agent, a catalyst, and a foam stabilizer. As a blowing agent, in order to suppress the recent stratospheric ozone depletion and the rise in surface temperature due to the greenhouse effect, it has been disclosed in JP-A-11-201628 and JP-A-11-248344 from the previous Freon. It has been changed to a rigid polyurethane foam using a mixed foaming agent of cyclopentane and water.

  However, cyclopentane and water tend to be disadvantageous in terms of heat insulation performance in the refrigerator-freezer employed because the thermal conductivity of the gas itself is larger than that of Freon.

  Thereafter, the thermal conductivity has been gradually improved as shown in, for example, JP-A-2003-42653 due to a change in the composition of the raw polyurethane foam, but the density has increased, and the refrigerator has become a refrigerator-freezer. The amount of rigid polyurethane foam injected tends to increase.

  On the other hand, in the building material field, polyurethane foam is partially used as a heat insulating board for wall surfaces, but there is an example in which a reinforcing material is used.

Japanese Patent Laid-Open No. 11-201628 Japanese Patent Laid-Open No. 11-248344 JP 2003-42653 A

  In recent years, energy conservation has been strongly desired from the viewpoint of global warming prevention, and energy conservation has become an urgent issue in all fields, and in refrigerators and refrigerators from the viewpoint of efficient use of heat. Adoption of rigid polyurethane foam having heat insulation performance is demanded.

  However, in recent years, crude oil prices and the imbalance between supply and demand for urethane raw materials around the world have prevented the worldwide tightening of urethane raw materials and the price of urethane raw materials from falling, and the manufacturing cost of refrigerators will continue to rise. It is a situation.

  Reducing the amount of urethane raw material used is effective in reducing the manufacturing cost of the above-mentioned soaring refrigerator and securing the urethane raw material required for refrigerator production. That is, the reduction of the injection amount of rigid polyurethane foam becomes a problem.

  However, as described in the previous section, the density of the foam tends to increase as an adverse effect of improving the performance of the rigid polyurethane foam, and the injection amount also tends to increase.

  Recently, in order to improve the internal volume of the refrigerator, there is a tendency to reduce the wall thickness of the refrigerator by using a combination of other high-performance heat insulating materials such as a vacuum heat insulating panel. Since the vacuum insulation panel is generally installed in the same space as the heat insulation space for injecting urethane, the space for the urethane resin to flow becomes narrow, so the fluidity of the urethane resin is lacking. This is an increase factor.

  As a result, recently, a low density type rigid polyurethane foam has been introduced, but there is a concern that the strength of the urethane resin may be lowered as a negative effect due to the lower density.

  Decrease in resin strength of rigid polyurethane foam leads to shrinkage and warping of the foam itself, and dents and distortions with the outer plate (iron plate) and inner plate (polystyrene resin, acrylonitrile butadiene styrene resin) of the refrigerator There was a problem that caused the appearance of the refrigerator.

  However, the characteristics of the urethane foam usually used in the cooling device field and the building material field of the present invention tend to be different. For example, the thermal conductivity, which is an index of heat insulation performance, is lower in the cooling device field than in the building material field. This is because glass wool, which has a relatively high thermal conductivity of about 3 times that of polyurethane foam, is still the mainstream in the building materials field, whereas the thermal conductivity is about 10% that of polyurethane foam in the cooling device field. Low heat conductivity is expected for polyurethane foams that also act as adhesives due to the fact that vacuum insulation materials with excellent low heat insulation performance have been actively used, limiting the composition of urethane raw materials The conditions are also great. In particular, in urethane formulations that pursue thermal conductivity, it is necessary to improve urethane reactivity and make the urethane bubble diameter finer, and the expansion after the foam is removed from the mold and the subsequent shrinkage increase, resulting in distortion. Tended to be larger. Further, in the heat insulating box of the refrigerator, particularly in the refrigerator, both the outer and inner urethane surfaces of the box are sandwiched by face materials having different linear expansion coefficients such as iron plate and plastic resin, and the shrinkage of the urethane foam It leads to distortion of plastic resin face material. Since the foam insulation board in the building material field is mainly concealed in the wall surface of the house, the board surface condition is not so limited. However, as for the cooling device, the double-sided material is the design surface of the product, and it is not allowed to impair the appearance.

  That is, in the cooling device field, compared with the building material field, a urethane formulation that can achieve higher performance and higher appearance quality is required, and among them, it is necessary to optimize the amount of reinforcing material blended.

  An object of the present invention is to improve the resin strength of a rigid polyurethane foam and to improve the appearance such as distortion and deflection.

  As a means for achieving the above-mentioned object, the present invention relates to a foaming agent such as polyether polyol, cyclopentane and water, and an auxiliary agent such as a catalyst and foam stabilizer in a rigid polyurethane foam used in a cooling device, particularly a refrigerator-freezer. In the collision mixing of the premixed liquid and the isocyanate liquid, the reinforcing material is mixed at a high pressure, so that the reinforcing material is contained in the rigid polyurethane foam and the strength physical properties of the rigid polyurethane foam are improved. As a result, the resin strength of the rigid polyurethane foam can be improved to achieve a low density while maintaining the appearance, and the injection amount of the rigid polyurethane foam can be reduced accordingly.

  The distortion of the design surface of the cooling device, particularly the refrigerator-freezer, can be attributed to the difference in the linear expansion coefficient between polyurethane foam, which is a heat insulator, and an iron plate or plastic resin that is bonded to both surfaces. In particular, polyurethane foam is a curable heat insulator, and the influence of the temperature factor on each is considered. As a mechanism for generating distortion, the polyurethane foam in the center is in contact and hardens from the low-temperature double-sided material side, that is, from the skin side. Yes. Deflection starts from the cooled skin side, and since it is bonded, the face material also starts to deform in a bimetallic state, and the foam center is then cooled and hardened. That is, it is considered that the difference in cooling time between the surface portion and the central portion affects the shrinkage of the foam, leading to distortion.

  Here, in the present invention, the reinforcing material is a material without a reinforcing material, that is, a material having high thermal conductivity as compared with a foaming agent such as cyclopentane existing in the foamed foam, and these are foamed urethane foam. By being present in the inside, heat is easily transferred to each reinforcing material, and heat transfer tends to be improved as a whole foam system. Thereby, the difference of the cooling rate of the skin side (surface side) and center part of a foaming urethane foam becomes small, and it becomes the tendency for a temperature difference to decrease. As a result, the amount of deformation of the foamed urethane foam is reduced, and the distortion due to this tends to be suppressed.

  Further, by optimizing the content of the reinforcing material, the box body and the door body can be thinned by increasing the strength while maintaining the low thermal conductivity of the rigid polyurethane foam. Since the space inside the refrigerator becomes larger due to such thinning, the present invention makes it possible to increase the volume of the refrigerator without significantly deteriorating the heat insulation performance while maintaining the external dimensions of the refrigerator. .

  A preferred specific configuration example of the present invention is as follows.

In the cooling device formed by filling a space formed between the outer box and the inner box with a rigid polyurethane foam using a mixed foaming agent of polyol, isocyanate, and cyclopentane and water,
(1) The hard polyurethane foam of the heat insulator contains a reinforcing material other than the hard polyurethane foam.
(2) The reinforcing material is made of an organic or / and inorganic material having a thermal conductivity larger than that of rigid polyurethane foam and exhibiting a needle shape, a plate shape, and a spherical shape.
(3) The reinforcing material is contained in an amount of 20 to 40% by weight based on the total weight of the urethane foam including a foaming agent and an auxiliary agent.
(4) The reinforcing material should contain a length of 300 μm or less and a cross section having a maximum length of 20 μm or less.

  Here, as the reinforcing material, as the needle-shaped material, inorganic fibers such as glass fiber, alumina fiber, carbon fiber, polyvinyl alcohol fiber, polyamide fiber, polyvinylidene chloride fiber, polyvinyl chloride fiber, Synthetic chemical fibers such as acrylic fibers and polyester fibers, and natural plant fibers such as cotton, ganpi, mitsumata, kenaf hemp, banana, pineapple, coconut palm, manila hemp, sisal hemp and jute are preferred. In addition, mica and glass flakes may be used as plate-like materials, glass spheres and glass hollow spheres may be used as spherical ones, and calcium carbonate and talc, wood powder, rubber scraps and the like may be used as others.

  If the rigid polyurethane foam of this invention is used, while reducing the usage-amount and reducing a cost, the refrigerator refrigerator which can improve a refrigerator external appearance can be provided.

  Hereinafter, embodiments of the present invention will be described.

  The manufacturing method of the refrigerator-freezer of this embodiment forms the heat insulation box 7 which consists of the outer box 13 and the inner box 14, and is in the space formed between the outer box 13 and the inner box 14 of this heat insulation box 7. The heat insulation box 7 is formed by filling the rigid polyurethane foam 11 with the vacuum heat insulation panel 12 disposed.

  And in this embodiment, the raw material of the rigid polyurethane foam by 2 components of the polyol component and isocyanate component comprised by mixing foaming agents represented by cyclopentane, water, etc., and auxiliary agents, such as a catalyst and a foam stabilizer. Is used.

  Here, the reinforcing material in the present invention is contained by impact-mixing the two-component raw material of the rigid polyurethane foam under high pressure.

  According to this embodiment, the amount of hard polyurethane foam 11 used can be suppressed in the heat insulation box 7 or the heat insulation box 7 mounted with the vacuum heat insulation panel 12, and the appearance of the refrigerator is improved. A refrigerator can be manufactured. The specific reason why such an effect is obtained will be described below.

  In the heat insulating box manufacturing method of this embodiment, as shown in FIG. 1, two liquids of polyol 1 and isocyanate 2 stored in separate containers are stirred by a mixing head 3, and a stirred urethane stock solution 5 is injected into an injection head 9. It inject | pours in the heat insulation box 7 made into more object.

  An example of a foaming process by filling a urethane stock solution 5 in which two liquids are stirred into a mold is shown. Here, the two liquids used for foaming are polyol 1 and isocyanate 2. However, the present invention is not limited to this, and the mold can also have any shape.

  In the case of pouring into the heat insulation box 7, as shown in FIG. 1, it falls downward according to gravity, then rises upward in the heat insulation box 7 while increasing the volume by foaming, and flows into the heat insulation box 7 as a whole. Then, the rigid polyurethane foam 11 is filled between the outer box 13 or the vacuum heat insulating panel 12 and the inner box 14.

  An example of the urethane foaming method of a door body is shown in FIG. Use a foaming mold that can hold the design iron plate side and liner side of the door separately in the upper and lower parts, but inject the urethane stock solution 5 into the lower design iron plate side of the foam mold that has been opened in advance. After completion, the upper mold holding the liner is closed and flows into the entire door body by foaming, and the rigid polyurethane foam 11 and the liner rising upward in the thickness direction of the door body are finally bonded to form an integral structure to be filled. Complete.

  Here, in order to simply evaluate the urethane foaming behavior in a box or door, the bending strength, bending elastic modulus, and dimensional change rate of a rigid polyurethane foam produced using the mold shown in FIG. 2 were measured. .

  As a reinforcing material used in this evaluation, a glass fiber crushed and powdered was used. About glass fiber reinforcement, the fiber length was made into the range of 30-350 micrometers, and the fiber diameter was made into the range of 10-50 micrometers. Moreover, the addition amount of the glass fiber reinforcing material was 5 to 50% of the total urethane foam stock solution weight. The case where more fillers are added is also assumed, but if the amount of filler is too large, the liquid viscosity will rise abnormally and stirring will not remain, so it is excluded from the study. In the first place, the liquid viscosity of the polyol solution has a great influence upon the reaction with the isocyanate liquid. If the liquid viscosity is high, the compatibility with the foaming agent will be low, so it will lack storage stability and affect the urethane foaming efficiency and heat insulation performance. There is a background that makes it possible to mix more. From these, considering the performance and productivity of the rigid urethane foam produced, a significant increase in the liquid viscosity should be avoided, but generally the liquid viscosity tends to increase when foreign matter is mixed in. It is necessary to have a mixing method that suppresses the increase in the amount of water as much as possible.

  About the rigid polyurethane foam of the reinforcing material produced on said various conditions, the bending elastic modulus was measured based on JIS specification. In that case, it represented with the index difference with the value of the bending elastic modulus of the rigid polyurethane foam produced without using the reinforcing material as 100. Moreover, about the cut sample cut out to 200x200x35 from the rigid polyurethane foam produced similarly, it measured with the heat conductivity measuring device (made by Eihiro Seiki Co., Ltd.). In that case, it represented with the index difference with the value of the heat conductivity of the rigid polyurethane foam produced without using the reinforcing material as 100.

  Here, FIG. 3 shows the relationship between the flexural modulus and the thermal conductivity of the reinforcing material blended when the length of the reinforcing material is set to 100 μm and the cross-sectional diameter is set to 10 μm.

  From FIG. 3, it can be seen that the flexural modulus increases as the blending amount of the reinforcing material increases. In particular, it can be seen that the flexural modulus is greatly improved when the blending amount is 20 wt% or more.

  On the other hand, the thermal conductivity is not greatly deteriorated while the amount of the reinforcing material is small, but it is understood that the thermal conductivity is relatively large when the amount is 50 wt% or more. This is considered to be because heat transfer increases along the fiber because the amount of the reinforcing fiber increases in the rigid polyurethane foam resin.

  From the above, it can be said that the blending amount of the reinforcing material is preferably 20 to 40 wt% in order to achieve high performance in a balanced manner with respect to the respective factors of bending elastic modulus and thermal conductivity.

  Next, the flexural modulus of the length of the reinforcing material and the viscosity of the urethane raw material when the reinforcing material compounding amount is fixed to 30 wt%, which is the preferable mixing amount range found earlier, and the reinforcing material diameter is fixed to 20 μm. FIG. 4 shows the relationship between the

  Here, if the length of the reinforcing material is theoretically increased, it can be easily estimated that the flexural modulus increases, but the reinforcing material rate in the urethane raw material increases accordingly, and the viscosity of the urethane raw material increases. It is conceivable to cause a problem at the time of the first impact mixing that causes a urethane curing reaction. Here, the value of the flexural modulus of the rigid polyurethane foam produced without using the reinforcing material and the value of the viscosity of the urethane raw material are set to 100, and the correlation between them is expressed as an index.

  FIG. 4 shows that the bending elastic modulus and the urethane raw material viscosity increase as the length of the reinforcing material increases. In particular, regarding the viscosity index, it can be seen that the length of the reinforcing material increases rapidly when the length of the reinforcing material is 350 μm or more. Further, the bending elastic modulus does not tend to be extremely different from 300 μm even at 30 μm, and therefore, the length of the reinforcing material is preferably 300 μm or less in consideration of the correlation with the viscosity of the urethane raw material.

  The present invention realizes a refrigerator-freezer with a small amount of urethane injection or a large refrigerator-free space by applying it to a heat-insulating box and a door of a refrigerator-freezer. Vacuum insulation is often used for the purpose of improving the power consumption and reducing power consumption. Vacuum insulation material is formed by inserting a core material molded from inorganic or organic fibers or foamed resin into an outer packaging material in which a metal foil or resin layer is laminated, and then evacuating the outer packaging material. However, the outer packaging material is extremely thin in order to minimize the heat wraparound.

  That is, by adding a reinforcing material as in the present invention, if the length or diameter of the reinforcing material is too large, for example, the surface of the vacuum heat insulating material may be damaged by the reinforcing material during polyurethane flow. The heat conductivity of the vacuum heat insulating material whose surface of the outer packaging material is damaged and a hole is opened and the vacuum inside the outer packaging material becomes atmospheric pressure becomes the original heat conductivity of the core material, and the heat of the rigid polyurethane foam It becomes worse than conductivity.

  From the above viewpoints, it can be said that the length of the reinforcing material is preferably 300 μm or less, considering not only the improvement of the flexural modulus but also the overall consideration.

  Next, the bending elastic modulus with respect to the size of the diameter of the reinforcing material when the amount of the reinforcing material is fixed to 30 wt%, which is the preferable mixing amount range found earlier, and the length of the reinforcing material is fixed to 200 μm. FIG. 5 shows the relationship between the amount of urethane and the amount of urethane injected.

  FIG. 5 shows that the flexural modulus and the amount of urethane injection increase as the diameter of the reinforcing material increases. In particular, with regard to the injection amount index, it can be seen that the diameter of the reinforcing material suddenly increases with a boundary of 20 μm. In addition, the flexural modulus is rapidly increased up to 20 μm, but it can be seen that the strength improvement is decreasing after 20 μm. Therefore, considering the bending elastic modulus and the amount of urethane injection, the diameter of the reinforcing material is preferably 20 μm or less.

  In this case as well, the diameter of the reinforcing material does not need to be unnecessarily increased because the influence of the puncture or damage to the outer packaging material on the surface of the vacuum heat insulating material is considered by increasing the diameter, as in the previous discussion.

  In addition, as described above, in the refrigerator-freezer field, there is a trend to increase the volume in the cabinet, and the wall thickness is becoming thinner. In order to mount a vacuum heat insulating material in the thin heat insulating space, the flow region of the hard polyurethane is extremely thin. Therefore, if the frictional force during flow with the outer iron plate of the refrigerator / freezer and the inner molding resin or vacuum heat insulating material is not reduced, the amount of urethane injection will increase, and the molding situation of rigid polyurethane foam is not preferable and originally retained Sufficient heat insulating properties cannot be exhibited.

  From the above viewpoints, it can be said that the diameter of the reinforcing material is preferably 20 μm or less, considering not only the improvement of the flexural modulus but also comprehensive consideration.

The schematic diagram explaining the production | generation principle and filling state of the rigid polyurethane foam by 2 liquid mixing used for the heat insulation box which concerns on one Embodiment. The schematic diagram explaining the filling state of the rigid polyurethane foam of the heat insulation door body of this embodiment. Relationship between the amount of reinforcing material blended when the length and diameter of the reinforcing material are constant, and the flexural modulus index and thermal conductivity index of the resulting reinforcing foam. The figure which shows the relationship between the length of a reinforcing material, the bending elastic modulus index | exponent of the obtained reinforcement foam, and the viscosity (after mixing a reinforcing material) of a urethane raw material. The figure which shows the relationship between the diameter of a reinforcing material, the bending elastic modulus index | exponent of a reinforcement foam obtained, and a urethane injection quantity index | exponent.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Polyol 2 Isocyanate 3 Mixing head 4 Mold 5 Urethane stock solution 5 'Urethane stock solution flow 6 Inlet 7 Heat insulation box 8 Refrigerator product back 9 Injection head 10 Hard polyurethane foam cut sample 11 Hard polyurethane foam 12 Vacuum insulation panel 13 Outside Box 14 Inner box 15 Design iron plate 16 Liner 17 Reinforcing material

Claims (4)

In a cooling device provided with a heat insulating body formed by filling a space formed between an outer box and an inner box with a rigid polyurethane foam using a mixed foaming agent of polyol, isocyanate, and cyclopentane and water,
A cooling device characterized in that the rigid polyurethane foam of the heat insulator contains a reinforcing material other than the rigid polyurethane foam and has a flexural modulus of 15 MPa to 25 MPa.   2. The hard polyurethane foam according to claim 1, wherein the hard polyurethane foam is composed of an organic or / and inorganic material having a needle shape, a plate shape, and a spherical shape, which has a higher thermal conductivity than the hard polyurethane foam. A cooling device characterized in that it is filled with a rigid polyurethane foam having a low foam deformation amount and an improved foam cooling rate.   The cooling device according to claim 1, wherein the rigid polyurethane foam containing 20 to 40% by weight of the reinforcing material with respect to the total weight of the urethane foam including a foaming agent and an auxiliary agent is filled.   2. The cooling device according to claim 1, wherein the rigid polyurethane foam containing the reinforcing material having a length of 300 [mu] m or less and a largest cross section of 20 [mu] m or less is filled.

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