JPH0242101B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a soft or semi-rigid polyurethane foam, and particularly to a method for producing a polyurethane foam with improved hardness. It is known to fill flexible or semi-rigid polyurethane foams with foamed particles. For example, polyurethane foams filled with inorganic foamed particles such as Shirasu balloons or synthetic resin foamed particles such as expanded styrene are known. for example,
JP-A-50-117861 describes a flexible polyurethane foam filled with foamed polyolefin particles, and JP-A-57-185328 describes a flexible polyurethane foam filled with expanded particles made of crosslinked styrene-acrylonitrile copolymer. Polyurethane foam is listed. On the other hand, foamable synthetic resin particles are added to a reactive mixture, and when the reactive mixture is foamed and cured, the foamable synthetic resin particles are foamed under the foaming and curing temperature conditions to produce a foamed particle-filled polyurethane foam. Also known, for example, Tokkosho
It is described in Publication No. 47-25855 and Japanese Patent Application Laid-open No. 70467-1987. One of the purposes of filling a soft or semi-rigid polyurethane foam with foamed particles is to improve the hardness (expressed by ILD) specified in JIS K6401. It may also be effective in improving physical properties such as load-bearing properties and compression set, and in improving foam-breaking effects. It is known that the use of foamed particles is particularly effective in improving the hardness of flexible polyurethane foams. However, polyurethane foam filled with expanded particles has not been widely used due to a number of problems. One of the biggest problems is the difficulty in foam manufacturing. Expanded particles as fillers for polyurethane foams are extremely difficult materials to handle. Since the foamed particles have a much lower apparent specific gravity than the liquid raw material, it is difficult to uniformly mix them into the liquid raw material or the reactive mixture that is a mixture thereof. In particular, unlike ordinary powder fillers, it is not possible to pre-disperse it in a liquid raw material such as a polyol and then mix it with other liquid raw materials to produce a reactive mixture containing expanded particles. Generally, expanded particles are added and mixed into liquid raw materials at the same time as they are mixed, and a reactive mixture containing expanded particles is foamed and cured to obtain a polyurethane foam containing expanded particles. However, even in this case, the mixture of foamed particles may be uneven,
The foamed particles float on or near the surface of the reactive mixture, making it difficult to obtain a polyurethane foam in which the foamed particles are evenly distributed. Unlike manual foaming methods, which are carried out on a trial basis, in mechanical foaming methods, which are widely used in industry, it is very difficult to uniformly mix expanded particles into liquid raw materials at the same time. Unlike the method using foamed particles described above, unfoamed expandable particles as described in the above-mentioned Japanese Patent Publication No. 47-25855 are used, and the foaming is performed under the temperature conditions during foaming and curing of the reactive mixture. It is believed that a method of manufacturing expanded particle-filled polyurethane foams by foaming the particles will greatly improve the manufacturing difficulties described above. However, the use of the expandable particles (hereinafter referred to as expandable beads) described in this known example still has many problems. One of them is the particle size of the expandable beads. Even when a filler with a large particle size is dispersed in a liquid raw material, it tends to settle or float due to the slight difference in specific gravity between the liquid raw material and the expandable beads. Moreover, liquid raw materials containing large fillers cannot be passed through liquid piping, pumps, or mixing and discharging machines, and mechanical foaming methods cannot be applied. Therefore, a batch system using hand foaming is usually the only foam manufacturing method, and its industrial applicability is low. If the particle size of the expandable beads is made smaller, the low boiling point hydrocarbons and halogenated hydrocarbons impregnated in the beads will dissipate more, which may make it difficult to produce good expanded beads. The production of expandable beads itself is difficult. The ideal liquid raw material containing an expandable filler is a so-called polymer polyol in which fine synthetic resin particles are stably dispersed in a polyol. Polymer polyol is a type of polyol that is widely used as a raw material for polyurethane foam, and extremely fine synthetic resin particles are uniformly dispersed in the polyol. However, it is difficult to separate easily from polyol. Even if the dispersion stability is not as sufficient as that of a polymer polyol, it is desirable that a mixture of a liquid raw material such as a polyol and an expandable filler be easily dispersed into a uniform state by mild stirring even after being separated once. For this purpose, it is desirable that the expandable filler has sufficiently fine particles and that its specific gravity is hardly different from that of the liquid raw material. If this ideal is achieved, it would be possible to obtain a liquid raw material containing an expandable filler that can be applied with ordinary mechanical foaming methods in the same way as polymer polyols. Additionally, it is desirable that the amount of expandable filler used be as small as possible to achieve the desired effect. It is well known that as the loading of fillers such as expanded particles increases, certain physical properties of polyurethane foams tend to deteriorate. Therefore, in order to achieve the desired effect while minimizing the deterioration of other physical properties, it is desirable to have a compound that can achieve high effects with a small amount of addition. In the present invention, which will be explained below and whose main purpose is to improve the hardness of polyurethane foam, an expandable filler is desired which is highly effective in improving the hardness even when added in small amounts. The present inventor conducted various research studies in order to find a polyurethane foam filled with foamed particles that solved the above problems, and as a result, by using fine thermally expandable microcapsules, the inventors solved these problems and created an excellent foamed polyurethane foam filled with foamed particles. I found out that it is possible to obtain the form. The gist of the present invention is to provide a method for producing a soft or semi-rigid polyurethane foam using a polyol, a polyisocyanate, a blowing agent, and a catalyst as essential raw materials.
In the reactive mixture, heat-expandable microcapsules shelled with a synthetic resin having an average particle size of about 200 microns or less are present in a substantially non-expanded state, and the thermally expandable microcapsules are made of a synthetic resin shell under the foaming and curing temperature conditions of the reactive mixture. A method for producing a polyurethane foam, which comprises expanding microcapsules to produce a polyurethane foam containing expanded particles. In the present invention, the reactive mixture refers to a mixture immediately after mixing the above-mentioned essential raw materials. In addition, in the present invention, microcapsule-like expandable particles whose volume can be increased by foaming the encapsulated foaming agent by heat are called thermally expandable microcapsules, in order to distinguish them from foaming of polyurethane foam. This foaming of microcapsules is hereinafter referred to as "expansion," but there is no essential distinction between foaming and expansion. Further, hereinafter, polyurethane foam refers to flexible polyurethane foam or semi-rigid polyurethane foam unless otherwise specified. The above-mentioned reactive mixture can be rapidly foamed and hardened at room temperature or heated temperature conditions. Thermally expandable microcapsules need to be able to expand at the reaction temperature or applied temperature conditions. When the ambient temperature is normal, the internal temperature of the reactive mixture is usually about 60° C. or higher during foaming and curing, and the thermally expandable microcapsules can expand above this temperature. However, to achieve more uniform expansion of the thermally expandable microcapsules, it is preferred that the ambient temperature be about 60°C or higher. In the case of molding, the ambient temperature is the mold temperature. Therefore, in that case, the mold temperature is preferably about 60°C or higher, particularly about 80°C or higher. When the mold temperature is high, the internal temperature of the reactive mixture often becomes lower than the mold temperature during foaming and curing. The maximum mold temperature is not particularly limited, but is about 250°C or less, particularly about 200°C or less. The maximum expansion temperature of expandable microcapsules, that is, the temperature at which the highest expansion ratio can be achieved, is approximately 80 to 180.
It is preferable that it is ℃. This maximum expansion temperature is approximately
If the temperature is 80°C, the thermally expandable microcapsules can be sufficiently foamed at about 60°C. For example, even if the maximum expansion temperature is about 140°C, it may be possible to achieve an expansion ratio of about 10 times at about 100°C (however, in the case of thermally expandable microcapsules alone). The heat-expandable microcapsules of the present invention have shells made of synthetic resin, and expansion of the expansion agent and softening of the shell are essential requirements for expansion. Therefore, inorganic shelled microcapsules generally do not expand under the foamed polyol temperature conditions of the reactive mixture. The swelling agent is encapsulated in the microcapsules and usually exists in a liquid or solid state. Expanding agents that exist in a gaseous state are usually undesirable because their specific gravity is low. The expanding agent expands the microcapsules by vaporizing under foaming temperature conditions or by decomposing the agent to generate gas. The expanding agent is preferably a vaporizable expanding agent made of a low boiling point hydrocarbon, halogenated hydrocarbon, or the like. Suitably, the average particle size of the thermally expandable microcapsules is less than about 200 microns, particularly about 1 to 100 microns, and more preferably about 5 to 50 microns. When the average particle size is larger than about 200 microns, the dispersion stability with respect to liquid raw materials decreases as described above, and application to mechanical foaming becomes difficult. Although there is no particular lower limit for the average particle size,
It is not easy to manufacture microcapsules of 1 micron or less, and they tend to be economically difficult to use. The synthetic resin that forms the shell of the thermally expandable microcapsules must have an appropriate softening temperature, must not be easily eroded by the components of the reactive mixture, as well as the expanding agent contained therein, and must be made of polyurethane foam. It is necessary to have properties such as affinity with the matrix of The softening temperature is as described above. The second requirement is that, for example, in the case of a liquid hydrocarbon blowing agent, if the shell is made of a synthetic resin permeable to the blowing agent such as polystyrene, the blowing agent will easily escape, which is undesirable. This is because the shell before or after expansion or the expanding shell may be damaged if it is easily attacked by other components of the reactive mixture. The former is one of the essential requirements for thermally expandable microcapsules.
, and without it, it cannot function as a thermally expandable microcapsule (however,
After expansion, the expansion agent tends to diffuse). As described below, the latter is an essential requirement in the most preferred embodiment in which it is used by being pre-dispersed in a polyol. Polyurethane foam obtained by using heat-expandable microcapsules with shells made of synthetic resin that has low affinity with the polyurethane foam matrix tends to separate the expanded particles from the matrix, making it difficult to maintain good physical properties. It is. In this sense, synthetic resins such as polyethylene are not suitable as shell materials. Based on these requirements, the most preferred shell material is a homo- or copolymer of a chlorine-containing polymerizable monomer such as vinyl chloride or vinylidene chloride. Particularly preferred are copolymers of vinylidene chloride. Suitable comonomers in this case are at least one vinyl monomer such as acrylonitrile, styrene, (meth)acrylate, vinyl acetate, and vinyl chloride, and a small amount of a crosslinking agent may also be used in combination. As described below, it is preferable to use the thermally expandable microcapsules after being dispersed in a polyol or a component containing a polyol in advance. In order to improve the dispersion stability of this dispersion, the thermally expandable microcapsules must have an average particle size within a specific range and a specific gravity that is close to the specific gravity of a liquid raw material such as polyol. is preferred. The specific gravity of the liquid component is usually in the range of 0.9 to 1.5. In particular, polyols range from 1.0 to 1.1, while polyisocyanates and halogenated hydrocarbon blowing agents range from 1.2 to 1.1.
It is usually within the range of 1.5. Therefore,
The specific gravity of thermally expandable microcapsules is within the range of 0.9 to 1.5, especially when used after being dispersed in a polyol or a component containing it.
It is preferably within the range of 0.95 to 1.2. The method of making the thermally expandable microcapsules present in the reactive mixture is not particularly limited. For example, when mixing raw materials such as polyols and polyisocyanates, thermally expandable capsules can be mixed simultaneously or immediately after the reactive mixture is prepared. However, it is more preferable to mix it into the liquid raw material in advance. The thermally expandable capsules can be used by mixing them into the polyisocyanate in advance. However, from the viewpoint of handling, it is most preferable to mix it into the polyol before use. It can also be mixed in advance into a polyol component, ie, a mixture of components other than polyisocyanate, such as polyol, blowing agent, and catalyst. In this case, the thermally expandable microcapsules are considered to be in a dispersed state in the polyol, which is the main component. The polyol in which thermally expandable microcapsules are dispersed can be handled in the same manner as the polymer polyol, and even if it is in a separated state, it can be easily made into a dispersed state by stirring. The use of this dispersion facilitates its application in mechanical foaming processes similar to polymer polyols. The amount of thermally expandable microcapsules added is not limited, but if a large amount is added as described above, not only will the hardness improvement effect of the polyurethane foam not improve in proportion to the amount added, but other physical properties will be affected. Since undesirable effects become significant, it is usually appropriate to use 20% by weight or less based on the polyol. In order to exert the effect on hardness, the lower limit of the amount added is usually about 0.1% by weight based on the polyol. A more preferable range of addition amount is 0.5 to 10% by weight, particularly 1 to 5% by weight based on the polyol. This addition amount is characterized by being very small compared to the range described in the above-mentioned known examples, especially the addition amount described in the examples thereof. That is, the effect of improving the hardness of the polyurethane foam achieved by using thermally expandable microcapsules is extremely remarkable, and it is also advantageous that other physical properties of the polyurethane foam are less likely to deteriorate. In the present invention, the polyurethane foam is obtained from the essential raw materials of conventional polyurethane foam consisting of polyol, polyisocyanate, blowing agent, and catalyst and thermally expandable microcapsules.
Further, in many cases, a foam stabilizer is an essential raw material for ordinary polyurethane foam. Also in the present invention, the use of a foam stabilizer is almost an essential raw material. Examples of optional raw materials include antioxidants, ultraviolet absorbers, anti-yellowing agents, other stabilizers, colorants, flame retardants, fillers, and reinforcing fiber crosslinking agents (the polyol crosslinking agents will be discussed later). ,
There are foam breakers, etc. Any of these raw materials can be used depending on the purpose, and the amount added is usually small compared to polyols and polyisocyanates, excluding fillers. As the polyol, a polyol whose main component is a high molecular weight polyol having a hydroxyl value of about 10 to 120, particularly about 20 to 80, and a hydroxyl group number of 2 or more is suitable. Suitable high molecular weight polyols include polyether polyols and/or polyester polyols, but hydroxyl group-containing hydrocarbon polymers such as hydroxyl group-containing polybutadiene, polyether ester polyols, and other high molecular weight polyols may also be used together with or alone. . Particularly preferred are polyether polyols made of polyoxyalkylene polyols having oxyalkylene groups having 2 to 4 carbon atoms and polyether polyols in which a vinyl polymer is dispersed (ie, polymer polyols). In particular, polyoxypropylene polyols having 2 to 8 hydroxyl groups and a hydroxyl value of about 20 to 80,
Polyoxypropyleneoxyethylene polyols are suitable. In the latter case, the arrangement of the oxypropylene group and the oxyethylene group may be block-like or random, and the oxyethylene group may be located at the end or inside the oxyalkylene chain. This polyoxyalkylene polyol is an initiator having an active hydrogen atom having a valence of 2 or more, especially a polyhydric alcohol, an alkanolamine, a mono- or polyamine, a polyhydric phenol, an alkylene oxide having 2 to 4 carbon atoms, such as propylene oxide, ethylene oxide, Polyoxyalkylene polyols obtained by adding butylene oxide are preferred. In some cases, polyoxyalkylene polyols having a primary hydroxyl group with an oxyethylene group at the end or relatively hydrophilic polyoxyalkylene polyols having an oxyethylene group inside are often suitable. These polyoxyalkylene polyols are 2
More than one species can be used in combination, and it can also be used in combination with other high molecular weight polyols. As the polymer polyol, polymer polyols obtained by polymerizing acrylonitrile and/or styrene in these polyether polyols or unsaturated group-containing polyols are preferred. In addition to high molecular weight polyols, low molecular weight polyols, which are called crosslinkers or chain extenders, are sometimes used, especially in the production of semi-rigid polyurethane foams. Suitable low molecular weight polyols include polyols with a molecular weight of 400 or less, especially 200 or less, which are composed of divalent or higher polyhydric alcohols and alkanolamines, such as ethylene glycol, 1,4-butanediol, propylene glycol, diethanolamine, and triethanolamine. be. As the foaming agent, water and/or a low-boiling halogenated hydrocarbon are suitable, but foaming can be caused by stirring or the like using an inert gas such as air. Water and halogenated hydrocarbons can be used alone or in combination. Suitable halogenated hydrocarbon blowing agents include trichlorofluoromethane, dichlorodifluoromethane, and methylene chloride. As the catalyst, various tertiary amine catalysts, their salts, or organometallic compounds such as organotin compounds can be used alone or in combination. As a foam stabilizer, polysiloxane
Polyoxyalkylene block copolymers and other organosilicon compounds are suitable. As the polyisocyanate, aromatic, aliphatic, alicyclic, and other polyisocyanates and modified products thereof can be used. Aromatic polyisocyanates are particularly suitable, although other polyisocyanates may be used alone or in combination with aromatic polyisocyanates. Not only can aromatic polyisocyanates be used alone, but also two or more aromatic polyisocyanates can be used in combination.
Examples of aromatic polyisocyanates include tolylene diisocyanate, diphenylmethane diisocyanate, polymethylene polyphenyl isocyanate, naphthalene diisocyanate, and xylylene diisocyanate. Examples of other polyisocyanates include hexamethylene diisocyanate and hydrogenated tolylene diisocyanate. , hydrogenated diphenylmethane diisocyanate, and isophorone diisocyanate. Dimers, trimers, prepolymer-type modified products, carbodiimide-modified products, and other modified products of these polyisocyanates can also be used. Particularly preferably 2,4-tolylene diisocyanate, 2,6
- tolylene diisocyanate, such as tolylene diisocyanate, mixtures thereof, and 4,
Diphenylmethane diisocyanates such as 4'-diphenylmethane diisocyanate or isomer mixtures thereof. The method for producing polyurethane foam is not particularly limited, and may be produced by a one-shot method, a quasi-prepolymer method, a prepolymer method, or other methods. In these methods, thermally expandable microcapsules are added to the raw materials of polyurethane foam, especially polyols.
Although it is preferable to use the thermally expandable microcapsules by dispersing them in advance, they can be added so that the thermally expandable microcapsules are present in the reactive mixture prior to the step of producing the reactive mixture. For example, in the prepolymer method, thermally expandable microcapsules can be added to the prepolymer at the prepolymer stage. In the present invention, a flexible polyurethane foam is suitable as the polyurethane foam. This is because, in the field of flexible polyurethane foams, there is currently a desire to improve the hardness of the foams, and no effective and economical means for this purpose have been known. For semi-rigid foam, depending on the type and amount of crosslinking agent used,
Improving hardness is relatively easy, and the means of the present invention can also be an effective means. In producing the flexible polyurethane foam, molding, slab molding, and other molding methods may be employed as the molding method. In particular, molding is advantageous in that the expansion of the thermally expandable microcapsules can be adjusted by adjusting the mold temperature. For example, if the temperature at which the reactive mixture is foamed and cured is not sufficient to thermally expand the thermally expandable microcapsules, this can be solved by increasing the mold temperature. In particular, when a reactive mixture foams and hardens, the highest heat generation area is usually limited to its center, and the temperature at the periphery is lower, so it may be difficult to expand the thermally expandable capsule uniformly throughout the foam. Not a little. Adjusting mold temperature can easily solve these problems. Of course,
Even in slab molding and the like, thermally expandable microcapsules can be expanded uniformly by controlling the temperature of the curing furnace. EXAMPLES The present invention will be specifically explained below using Examples, but the present invention is not limited to these Examples. Examples and Comparative Examples Using a polyol in which thermally expandable microcapsules had been dispersed in advance, a flexible polyurethane foam was produced by hot molding using the one-hitch method. Two types of thermally expandable microcapsules, A and B below, are used, and the amount of each added is within the range of 1 to 10 parts by weight per 100 parts by weight of polyol. In addition, when the heat-expandable microcapsule-dispersed polyol is made into a uniform dispersion by stirring and left to stand still, it shows no tendency to separate at all for at least 3 days, and after about 1 month, some of the microcapsules float to the surface of the polyol. However, it could be easily redispersed by stirring. Thermal expandable microcapsule A: Product name: "Matsumoto Microsphere F-30"
[Manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd.] Average particle size: Approximately 15 microns (more than 95% of them are 5 to
(in the range of 30 microns) Shell material and softening temperature: Vinylidene chloride-acrylonitrile copolymer, 75-85℃ Expansion agent: Hydrocarbon expansion agent Maximum expansion ratio and temperature: approx. 75 times, approx. 135
℃ True specific gravity after drying: Approx. 1.02 Thermally expandable microcapsule B: Product name: "Matsumoto Microsphere F-50"
[Manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd.] Average particle size: Approximately 15 microns (more than 95% of them are 5~
(within the range of 30 microns) Shell material and its softening temperature: vinylidene chloride-acrylonitrile copolymer (however, the monomer composition ratio is different from thermally expandable microcapsule A), 100 to 105°C Expansion agent: carbonized Maximum expansion ratio of hydrogen-based expansion agent and temperature: approx. 20 times, approx. 140
°C True specific gravity after drying: approximately 1.02 The raw material molding conditions for producing flexible polyurethane foam are as follows. In addition, the amount of polyol and thermally expandable microcapsules added (polyol 100
Table 1 (Examples 1 to 8, Comparative Examples 1 to 8) shows the raw material composition (expressed in parts by weight), such as the amount added to parts by weight), and the physical properties of the obtained flexible polyurethane foams.
3). Similarly, production examples of semi-rigid polyurethane foam are shown in Table 2 as Examples 9 and 10 and Comparative Example 4. [Raw materials] Polyol A: polyoxypropylene, oxyethylene triol with a hydroxyl value of 53 and an oxyethylene group content of 18% by weight. Polyol B: Polyoxypropylene, oxyethylene triol with a hydroxyl value of 56 and an oxyethylene group content of 8% by weight. Polyol C: hydroxyl value 42, acrylonitrile
A polyether triol-based polymer polyol in which styrene copolymer is dispersed. Polyol D: polyoxypropylene, oxyethylene triol with a hydroxyl value of 34 and an oxyethylene group content of 14.5% by weight. Polyol E: A polyether triol-based polymer polyol with a hydroxyl value of 28 and in which acrylonitrile polymer is dispersed. Foam stabilizer: Organosilicon compound foam stabilizer (however,
Different foams are used for soft and semi-rigid foams). Catalyst A: Triethylenediamine catalyst (product name:
DABCO 33LV) Catalyst B: Stanus octoate Catalyst C: Amine-based catalyst different from Catalyst A Polyisocyanate A: 80/20 mixture of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate. Polyisocyanate B: crude diphenylmethane diisocyanate and polyisocyanate A
A mixture with a weight ratio of 1:1. (The amount of both polyisocyanates used is expressed in isocyanate index) [Physical properties] (according to JIS K6401 (1980), etc.) D: Density [Kg/m ³ ] ILD25%: Hardness (Kg/314cm ² ) BR: Repulsion modulus [%] Tr: Tear strength [Kg/cm 2 ] Ts: Tensile strength [Kg/cm ² ] EL: Elongation [%] SD: Compression set (dry) [%] [Molding conditions] Γ Soft polyurethane foam Mold: Aluminum, wall thickness 5mm Shape: 400 x 500 x 50mm Cure temperature x time: 150℃ x 12 minutes Mold temperature during demolding: 85±2℃ Γ semi-rigid polyurethane foam Mold: Aluminum, wall thickness 10mm Shape: 400×400×50mm Mold temperature during injection: 50℃ Curing conditions: Leave at room temperature, 4 minutes

【table】

【table】

【table】

【table】

Claims (1)

[Claims] 1. Polyol, polyisocyanate, blowing agent,
In a method for producing a soft or semi-rigid polyurethane foam using a catalyst as an essential raw material, heat-expandable microcapsules having a shell of a synthetic resin with an average particle size of about 200 microns or less and which are in a substantially non-expanded state in a reactive mixture. 1. A method for producing a polyurethane foam, which comprises producing a polyurethane foam containing expanded particles by expanding the thermally expandable microcapsules under the foaming curing temperature conditions of the reactive mixture. 2 Thermally expandable microcapsules have a synthetic resin shell, encapsulate a vaporizable expansion agent, and have an average particle size of approximately 1 to 100.
The method according to claim 1, characterized in that the microcapsules are thermally expandable microcapsules having a diameter of micron and a temperature at which the maximum expansion ratio can be achieved is about 80 to 180°C. 3 The thermally expandable microcapsules have a specific gravity of approximately
The method according to claim 2, characterized in that the temperature is between 0.9 and 1.5. 4. The method according to claim 1, wherein the amount of thermally expandable microcapsules added is 0.1 to 20 parts by weight per 100 parts by weight of polyol. 5. The method according to claim 1, characterized in that the thermally expandable microcapsules are used by being dispersed in a polyol in advance.