JPH022899B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a molding material for producing fiber-reinforced polyurethane, and particularly to a fiber-reinforced polyurethane molding material that is solid at room temperature and is suitable for press molding or injection molding. Molding materials that are solid at room temperature called SMC and BMC are known as molding materials for producing fiber-reinforced thermosetting resins. For example, molding materials obtained by blending reinforcing fibers and fillers with a liquid unsaturated polyester resin containing unsaturated polyester and styrene, and further adding a thickener to increase the viscosity are widely used. Magnesium oxide, magnesium hydroxide, etc. are used as the thickener.
This molding material is divided into SMC, which is a sheet-like molding material suitable for press molding, and BMC, which is a block-to-granular molding material suitable for injection molding, but their compositions are almost the same, and the blending methods are slightly different. It is something that One of the problems with conventional unsaturated polyester molding materials is that the impact resistance of molded products is low.
In order to improve this point, a method is known in which an impact resistance improver, for example, a polymer such as a synthetic rubber or an elastomer, is added to the molding material, but this method is still not satisfactory. For this reason, various attempts have been made to obtain similar molding materials using synthetic resins other than unsaturated polyester resins. Part 1
One attempt has been made to use polyurethane as a synthetic resin with high impact resistance. One of these attempts is to use unsaturated polyester as a polyol and produce a molding material containing this and polyisocyanate as main components. However, this molding material
As long as unsaturated polyester is used, impact resistance cannot be sufficiently improved. There is also a method of producing liquid unsaturated polyurethane using an unsaturated compound having a hydroxyl group such as hydroxyalkyl acrylate, and using this instead of unsaturated polyester to produce a molding material. However, when using a type of synthetic resin that is cured by addition polymerization of these unsaturated groups, it is not much different from conventional molding materials using unsaturated polyester, and sufficient impact resistance cannot be expected. Polyurethane-based molding materials that do not utilize curing by addition polymerization of unsaturated groups include those that utilize polyols that are solid at room temperature. Although the polyol, which is solid at room temperature, reacts with the polyisocyanate on the surface of the solid, it does not react inside the solid, and therefore the molding material has shelf life. During molding, the solid polyol melts and reacts with the polyisocyanate to obtain a molded product. However, this molding material is economically disadvantageous because it uses a special polyol, and there are also many problems in the manufacturing method and handling of the molding material. The present inventor considered obtaining the above-mentioned molding material using an ordinary liquid and substantially saturated polyol. The main problems in this case are considered to be thickening and storage stability. In order to make the raw material mixture into a solid molding material at room temperature, it is necessary to thicken it, but the thickeners used in the case of unsaturated polyester resins cannot be used. This is because the thickening mechanism is unique to unsaturated polyester and has no effect on polyurethane. Preservability refers to the ability of a molding material to be stored for a relatively long period of time without causing any changes over time. In the case of polyurethane, it is necessary to store the polyol and polyisocyanate in a mixed state for a relatively long period of time without reacting. As a result of studying these two problems, the present inventor found that the latter problem of storage stability could be solved by using blocked polyisocyanate as the polyisocyanate. Blocked polyisocyanates do not react with polyols unless their blocks come off, and during molding, the blocks come off and react with polyols. Therefore, there is little chance that the two will react and change in the molding material, and the same level of storage stability as conventional molding materials can be obtained. The problem of thickening in the former case is that unblocked polyisocyanate (hereinafter referred to as free polyisocyanate) is used as part of the polyisocyanate, and part or all of this free polyisocyanate is converted into polyol when producing the molding material. We discovered that this can be done by reacting with The amount of this free polyisocyanate must be below a certain limit; if the amount is too large, a good molding material cannot be obtained. The inventor further found that, in consideration of physical properties such as impact resistance of molded products, it is necessary to use a combination of high molecular weight (low hydroxyl value) polyols and low molecular weight (high hydroxyl value) polyols. I discovered something. The present invention relates to a molding material using these raw materials, that is, a molding material that is solid at room temperature and can be used to produce fiber-reinforced polyurethane by heat curing, in which the molding material contains polyurethane raw materials, reinforcing fibers, and fillers. It contains at least three components and is obtained by reacting and thickening a part of the polyurethane raw material, and the polyurethane raw material has blocked isocyanate groups and unblocked isocyanate groups that are the same. Alternatively, it consists of at least three components: a polyisocyanate in different molecules, a substantially saturated polyol with a hydroxyl value of 200 or more, and a substantially saturated polyol with a hydroxyl value of less than 200, in a blending amount based on the total isocyanate groups in the polyisocyanate. is equivalent to 50 to 95% of blocked isocyanate groups, 5 to 50% of unblocked isocyanate groups, and the isocyanate index of all polyisocyanates to all polyols is 80 to 200, and the hydroxyl value to all polyols is 200. The proportion of polyol is more than 20
The fiber-reinforced polyurethane molding material is characterized in that the proportion of polyol having a hydroxyl value of less than 200 is 5 to 80% by weight. The molding material can be manufactured using the same raw materials and manufacturing methods as conventional molding materials, except that polyurethane raw materials are used. For example, glass fiber is suitable as the reinforcing fiber, but carbon fiber, synthetic fiber, and other reinforcing fibers may be used alone or in combination. Examples of fillers used include calcium carbonate, clay, silica, aluminum hydroxide, and other powder fillers. As raw materials for the molding material, any other components may be added in addition to the above three components. For example, blowing agents,
Colorants, flame retardants, mold release agents, stabilizers, etc.
Although the proportion of each component is not particularly limited,
Suitable amounts are about 5-60% by weight of reinforcing fibers, about 10-70% by weight of fillers, and about 10-60% by weight of polyurethane raw materials, based on the molding material. The manufacturing method of molding material is as follows:
For example, conventional SMC manufacturing methods and BMC manufacturing methods can be applied almost as they are, but are not limited to these methods. The polyurethane raw material basically contains polyisocyanate and at least two kinds of polyols as main components. Small amounts of catalysts, stabilizers, chain extenders, crosslinking agents, and other additives may also be used as other auxiliary raw materials, if necessary. As the polyisocyanate, aromatic, aliphatic, alicyclic, and other polyisocyanates can be used. Typical polyisocyanates include, for example, tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), polymethylene polyphenyl isocyanate (PAPI), naphthalene diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and methylene diisocyanate. Bis(cyclohexyl isocyanate), etc. These may be used alone or in combination of two or more. Further, the polyisocyanate may be a so-called modified polyisocyanate that has been modified by various compounds or treatments. Examples include carbodiimide-modified polyisocyanates and prepolymer-type modified polyisocyanates. Some of the isocyanate groups in the polyisocyanate are blocked isocyanate groups, and the other part are free isocyanate groups, and the ratio is as follows with respect to the total isocyanate groups:
Blocked isocyanate groups expressed by number
50-95%, free isocyanate groups 5-50%. The blocked isocyanate group and the free isocyanate group may be present in one molecule, in different molecules of the same type, or in different molecules of different types. for example,
One isocyanate group in one molecule of MDI may be blocked and the other isocyanate groups may be free groups. Preferably, for example, both of the two isocyanate groups are blocked.
A combination of different molecules of the same type, such as a mixture of MDI and MDI, both of which are free isocyanate groups, or a mixture of, for example, MDI, both of which are blocked, and TDI, both of which are free groups. Preferably, the main component is a combination of different types of molecules. In the latter case, different types of polyisocyanates include combinations of modified polyisocyanates and unmodified polyisocyanates of the same type. This polyisocyanate containing both isocyanate groups can be prepared by adding a predetermined amount of a blocking agent to a polyisocyanate containing free isocyanate groups;
It can be produced by mixing unblocked polyisocyanate and free polyisocyanate, or by various other methods. The proportion of both isocyanate groups is within the above range, but more preferably 60-80% of blocked isocyanate groups and 20-40% of free isocyanate groups.
It is. As the blocking agent, various blocking agents used for blocking isocyanate groups can be used. For example, isopropanol, trimethylolpropane, 1,3-dichloro-2-propanol, other alcoholic blocking agents, phenol, cresol, catechol, nitrophenol, other phenolic blocking agents, ε
- Caprolactam, other lactam blocking agents, acetone oxime, methyl ethyl ketone oxime, methyl isoamyl ketone oxime, methyl isobutyl ketone oxime, other oxime blocking agents, malonic acid ester, acetoacetic ester, other active methylene blocking agents agents, but are not limited to these. In the present invention, the polyol used is a combination of a polyol with a relatively high hydroxyl value and a polyol with a relatively low hydroxyl value. As the polyol, polyether polyols, polyester polyols, polyhydric alcohols, and various other polyols can be used, but polyether polyols are particularly preferred. As this polyol, a substantially saturated polyol is used. The molding material of the present invention is not of the type in which curing is performed using addition polymerization of unsaturated groups in polyol or polyurethane. Therefore, there is no particular problem in using polyols having unsaturated groups, but
There is no need to intentionally introduce unsaturated groups into the polyol. Substantially saturated polyether polyols include polyether polyols obtained by adding an epoxide to an initiator having at least two hydrogen atoms to which epoxides can be added (hydrogen atoms such as hydroxyl groups and amino groups); These include ring-opening polymers of cyclic ethers having more than one member ring. Suitable initiators include polyhydric alcohols, polyphenols, polyamines, alkanolamines, and other initiators having hydroxyl groups, amino groups, amide groups, and the like. Examples of initiators include the following: Polyhydric alcohols: ethylene glycol, propylene glycol, dipropylene glycol, glycerin, trimethylolpropane, diglycerin, pentaerythritol, dextrose,
Sorbitol, sucrose polyphenols: Novolac, bisphenol A, bisphenol S Polyamines: ethylenediamine, tolylene diamine, diaminodiphenylmethane alkanolamines: monoethanolamine, diethanolamine, triethanolamine, diisopropanolamine Epoxides include alkylene oxide , halogen-containing alkylene oxide, glycidyl ester, glycidyl ether, styrene oxide,
There are other epoxides, especially those with 2 to 4 carbon atoms.
alkylene oxides are suitable. Particularly preferred as the epoxide are propylene oxide and/or ethylene oxide. Polyether polyols obtained by adding propylene oxide alone or propylene oxide and other epoxides to an initiator may become polyether polyols containing a small amount of unsaturated groups due to side reactions of the propylene oxide addition reaction. Are known. The substantially saturated polyether in the present invention may be a polyether polyol containing a small amount of unsaturated groups. In addition, for the purpose of polyether polyols in which all or part of the terminal hydroxyl groups of polyether polyols are primaryized, that is, ethylene oxide is added to the terminals, and polyether polyols in which oxyethylene groups are present in the polyether chain. It can also be used accordingly. As polyols other than polyether polyols, polyester polyols, polyether ester polyols, hydrocarbon polymers having two or more hydroxyl groups, polycarbonate polyols, polyhydric alcohols, alkanolamines, etc. can also be used. In the present invention, at least two types of polyols as described above are used. One is a polyol with a high hydroxyl value, and the other is a polyol with a low hydroxyl value. The polyol having a high hydroxyl value is suitably one having a hydroxyl value of 200 or more, particularly 300 to 800.
Polyols with a low hydroxyl value are suitably those having a hydroxyl value of less than 200, particularly from 20 to 150. When the hydroxyl values of the two polyols are close, the difference between the two is preferably 50 or more. Furthermore, in the case of a mixture of polyols in which at least one of the polyols has a different hydroxyl value, these hydroxyl values shall indicate an average hydroxyl value. The proportion of both polyols is 20 to 95% by weight of the polyol with a high hydroxyl value and 5 to 80% by weight of the polyol with a low hydroxyl value, more preferably 60 to 80% by weight of the polyol with a high hydroxyl value, based on the total polyol.
95% by weight, 5-40% by weight of low hydroxyl value polyol
It is. The ratio of these two polyols is necessary from the viewpoint of the physical properties of the fiber-reinforced polyurethane, such as rigidity and impact strength, and if it is outside this range, it will be difficult to obtain a molded product with good physical properties. As mentioned above, in the molding material of the present invention, the polyurethane raw material is thickened due to the formation of a part of the polymer through the reaction between free isocyanate groups and polyol, and as a result, a molding material that is solid at room temperature can be obtained. The degree of this thickening depends on the amount of free isocyanate groups, and the larger the amount, the more the thickening progresses. Therefore, the degree of thickening can be adjusted within the range of the proportion of free isocyanate groups. The blocked isocyanate groups are stable, and therefore the viscosity changes little after the thickening is almost completed, ensuring storage stability.
When molding the molding material of the present invention, the blocking agent is removed from the blocked isocyanate by the heat during molding, becomes free isocyanate groups, and reacts with the polyol to produce the desired polyurethane. As with conventional SMC and BMC, molding can be performed using various methods such as press molding, injection molding, and extrusion molding. Particularly suitable are press molding and injection molding.
In the case of press molding, a molded product reinforced with relatively long reinforcing fibers can be obtained. Therefore, in order to exhibit this feature, the reinforcing fibers in the molding material are preferably relatively long, with an average length of about 1
It is preferable to use a diameter of 5 mm or more, particularly about 5 mm or more. There is no particular upper limit, and continuous fibers of almost infinite length, such as glass fiber rovings or continuous strand mats, can be used. On the other hand, in the molding material used for injection molding, it is difficult to use reinforcing fibers that are too long, and a length of about 1 to 10 mm is usually appropriate. For example, in the case of glass fibers, chopped strands or milled fibers having an average length of this length are suitable. EXAMPLES The present invention will be specifically explained below using Examples, but the present invention is not limited to these Examples. Example 1 10 parts of a polyol with a hydroxyl value of about 100 (parts by weight: the same applies hereinafter) obtained by adding propylene oxide to glycerin and 90 parts of a polyol with a hydroxyl value of about 500 obtained by adding propylene oxide to seurose. a prepolymer-type modified 4,4'-diphenylmethane diisocyanate (NCO content 25%) in an amount that gives an isocyanate index of 20 to the mixed polyol, and an amount that gives an isocyanate index of 90 to the mixed polyol. A mixture of phenol-blocked hexamethylene diisocyanate (NCO content 10%) and calcium carbonate in an amount to give a final loading of 35% were mixed. Immediately apply this mixture to the surface of the film, and spread it over an average length of approximately 35% by weight.
Glass fibers of 50 mm were dispersed, and another film coated with the above mixture was layered on top of the glass fibers, and the film was aged to produce a sheet-like molding material that was solid at room temperature. This molding material was moldable for at least 30 days. This molding material was pressed for 20 minutes at a mold temperature of 180°C to produce a flat molded product. The density of the molded product is
The strength was 1.8Kg/cm ³ , the isot strength was 98Kg·cm, and the bending strength was 18Kg/mm ² . Example 2 Polyol mixture of the same type and amount as in Example 1,
Similarly, polyisocyanate, calcium carbonate in a final blending amount of 50% by weight, and glass fibers with an average length of about 5 mm in a final blending amount of 15% by weight were mixed and kneaded in a kneader to form a lump molding material. Manufactured. This molding material was moldable for at least 30 days. The injection pressure of this molding material was 400Kg/ ^cm2 , and the mold temperature was 180Kg/cm2.
Injection molded at ℃. The density of the obtained molded product is 1.9
Kg/cm ³ , Izotsu strength is 85Kg・cm, bending strength is
It was 12Kg/ ^mm2 . Examples 3 to 5, Comparative Examples 1 and 2 Sheet-shaped molding materials (Example 3,
4, 6, 7, 8) and a bulk molding material (Example 5) were produced. Table 1 shows the physical properties of molded products obtained by press molding (Examples 3, 4, 6, 7, and 8) and injection molding (Example 5) using each molding material. On the other hand, Table 1 also shows examples in which a conventional unsaturated polyester sheet molding material was press-molded and examples in which an unsaturated polyester bulk molding material was injection molded as Comparative Examples 1 and 2.

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Claims (1)

[Claims] 1. A molding material that is solid at room temperature and can be used to produce fiber-reinforced polyurethane by heat curing, which contains at least three components: a polyurethane raw material, reinforcing fibers, and a filler, and which is increased by a reaction with a part of the polyurethane raw material. The polyurethane raw material is a polyisocyanate having blocked isocyanate groups and unblocked isocyanate groups in the same or different molecules, and a substantially saturated polyisocyanate with a hydroxyl value of 200 or more. Consisting of at least three components: a polyol and a substantially saturated polyol with a hydroxyl value of less than 200, the amount of blocked isocyanate groups in the polyisocyanate is equivalent to 50 to 95% of the total isocyanate groups, and unblocked isocyanate groups. 5 to 50% isocyanate groups, and the isocyanate index of all polyisocyanates to all polyols is 80 to 200, and the ratio of polyols with a hydroxyl value of 200 or more to all polyols is 20
A fiber-reinforced polyurethane molding material characterized in that the proportion of polyol having a hydroxyl value of less than 200 is 5 to 80% by weight.