JPH0621147B2 - Manufacturing method for rigid polyurethane foam - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method for producing a rigid polyurethane foam, in particular a void- and shearline-free rigid polyurethane foam produced by cast foaming.

(Prior Art) Since rigid polyurethane foam has excellent heat insulating properties, it is used for keeping heat and cooling in houses, warehouses, etc., as well as for sandwich panels, core materials for outer boxes of electric refrigerators, etc. In addition, it is used in various areas as a casing material for furniture and equipment with an uneven surface pattern.

When manufacturing a rigid polyurethane foam, a method of injecting a stock solution into a void of a female mold or an object and foaming and curing is generally performed. Recently, these construction objects have become large in size, and many obstacles such as pipes are present in the voids, and they have become complicated in shape. In addition, the complicated and elaborate patterns for the outer surface of furniture, casings, etc. are required. Furthermore, the demand for products having a high surface smoothness is very high.

In addition to increasing the size of the injection target and complicating the shape, it is required to shorten the mold rotation time and enhance work efficiency. The low-pressure system has been switched to a high-pressure injection foaming machine to rapidly inject a large amount of stock solution.

(Problems to be solved by the invention) When a stock solution is injected into a large and complicated object and foaming and hardening are rapidly performed, crude diphenylmethane diisocyanate and a polyol are usually prepared by a one-shot method in the presence of a catalyst. The method of making it react is performed.

At this time, the undiluted solution in the middle of foaming entrained air, cell association,
Alternatively, gas remains due to cell collapse, resulting in voids.

The undiluted solution during foaming causes an abnormal flow at the tip of its expansion due to friction with the wall surface of the void, and the bubbles become coarse to form a so-called share line. The presence of such voids or shear lines significantly reduces the properties and commercial value of the rigid polyurethane foam, which is a serious problem.

(Means for Solving Problems) As a result of various investigations by the present inventors for eliminating voids and shear lines, 4,2 ′ was obtained as polyisocyanate.
5 to 50% by weight of diphenylmethane diisocyanate
The present inventors have found that it is effective to use the contained crude diphenylmethane diisocyanate, and have reached the present invention.

That is, the present invention is as follows.

In the method for producing a rigid polyurethane foam by reacting a polyisocyanate, a polyol, a catalyst, a foam stabilizer and, if necessary, other additives, 4,2'-diphenylmethane diisocyanate is added as a polyisocyanate in an amount of 5 to 5.
A method for producing a rigid polyurethane foam, which comprises using 50% by weight of crude diphenylmethane diisocyanate.

The crude diphenylmethane diisocyanate used for the production of rigid foams is usually 4,4'-diphenylmethane diisocyanate 35-65% by weight, 4,2'-diphenylmethane diisocyanate 0-5% by weight, methylene cross-linked polyphenyl polyisocyanate having 3 or more functional groups. (Hereinafter abbreviated as polynuclear body) 65 to 35% by weight.

The crude diphenylmethane diisocyanate used in the present invention is 4,2′-diphenylmethane diisocyanate 5 to
It is used as a polyisocyanate composed of 50% by weight, 60 to 30% by weight of 4,4'-diphenylmethane diisocyanate, and 65 to 35% by weight of a polynuclear body. The particularly preferred content of 4,2'-diphenylmethane diisocyanate is 10 to 30% by weight.

In the injection and foaming of polyurethane, in order to prevent the occurrence of voids by causing the undiluted solution in the undiluted solution to enter every corner of the void, it is necessary to suppress the increase in viscosity until the final stage of foaming. In addition, it is necessary to suppress the increase in viscosity in order to reduce the friction between the inner surface of the void and the foaming undiluted solution and narrow the range in which the shear line is generated. Further, it is necessary to increase the compatibility between the crude diphenylmethane diisocyanate and the polyol for uniform foaming.

When 4,2′-diphenylmethane diisocyanate is added to and mixed with the crude diphenylmethane diisocyanate, the compatibility between the crude diphenylmethane diisocyanate and the polyol can be increased while suppressing an increase in the viscosity of the stock solution during foaming.

Thus, 4,2'-diphenylmethane diisocyanate has an excellent effect, but when the content in the polyisocyanate is 5% by weight or less, the effect is not recognized, and when it exceeds 50% by weight, it becomes difficult to control the foaming conditions. Become.

Examples of the polyol used in the present invention include ethylene glycol, propylene glycol, diethylene glycol,
Triethylene glycol, dibropyrene glycol, glycerin, trimethylolpropane, 1,3,6-hexanetriol, pentaerythritol, sorbitol, sucrose, bisphenol A, novolac, hydroxylated 1,2-polybutadiene, hydroxylated 1,4
A polyhydric alcohol such as polybutadiene, and / or a polyether polyol having a hydroxyl value of 200 to 800 mgKOH / g obtained by addition-polymerizing an alkylene oxide to these polyhydroxy compounds. Also, alkanolamines such as diethanolamine and triethanolamine,
A compound containing two or more active hydrogens such as ethylenediamine, diethylenetriamine, ammonia, aniline, tolylenediamine, xylylenediamine, and diaminodiphenylmethane, and / or these amines, ethylene oxide, propylene oxide, butylene oxide, styrene oxide, etc. It is also possible to use a polyether polyol having a hydroxyl value of 200 to 800 mg KOH / g and a polytetramethylene ether glycol obtained by addition polymerization of

In addition to the above, higher fatty acid ester polyols and polyester polyols obtained by reacting a polycarboxylic acid with a low molecular weight polyol and polyester polyols obtained by polymerizing caprolactone, castor oil, OH group-containing higher fatty acid esters such as dehydrated castor oil are also available. Can be used.

Catalysts useful in the present invention include, for example, N, N, N ', N'-
Tetramethyl-hexamethylenediamine, pentamethyldiethylenetriamine (PMDETA), dimethylpalmitylamine, trimethylaminoethylpiperazine, triethylamine, triethylenediamine, N, N, N ', N'-tetramethylpropanediamine, N, N, N ′, N′-Tetramethylhexamethylenediamine (TMHD), N, N, N ′, N ′
-Tetramethyl-1,3-butanediamine, N, N'-dimethylcyclohexylamine, bis (2-dimethylaminoethyl) ether, N, N ', N "-tris (dimethylaminoethyl) hexahydrotriazine, N , N ′, N ″ −
(Diethylaminopropyl) hexahydrotriazine,
2,4-bis (dimethylaminomethyl) phenol, 2,
4,6-Tris (diethylaminomethyl) phenol, amines such as tetramethyl guanidine, tin octoate, tin oleate, dibutyltin dilaurate, lead naphthenate, cobalt 2-ethylhexanoate, potassium acetate,
Organic metal compounds such as sodium propionate and potassium octanoate.

In the present invention, a foaming agent and a foam stabilizer are used to form a foam.

As the foaming agent, water, trichloromonofluoromethane,
One or more of dichlorodifluoromethane, methylene chloride, trichlorotrifluoroethane, dibromotetrafluoroethane, trichloroethane, pentane, hexane and the like are used.

The foam stabilizer in the present invention is a conventionally known organic silicon surfactant, for example, L-501, L manufactured by Nippon Unicar Co., Ltd.
-520, L-532, L-540, L-544, L-3550, L-53
02, L-5305, L-5320, L-5340, L-5350, L-54
10, L-5420, L-5421, L-5710, L-5720, etc., and SH-190, SH-192, SH- manufactured by Torre Silicone Co.
193, SH-194, SH-195, SH-200, SRX-253, and the like, manufactured by Shin-Etsu Silicone Co., Ltd. F-114, F-121, F-12.
2, F-220, F-230, F-258, F-260B, F-305,
F-306, F-317, F-341, F-601, F-606, X-2
0-200, X-20-201, etc., and TFA-4200, TFA-4202, etc. manufactured by Toshiba Silicone Co., Ltd.

Further, as a flame retardant, for example, tris (2-chloroethyl)
Phosphate, tris (dichloropropyl) phosphate, tris (dibromopropyl) phosphate, Daihachi Chemical Co., Ltd. CR-505 and CR-507, Monsanto Chemical Co., Pho
ogard 2XC-20 and C-22-R, F by Stopher Kagaku
yrol 6 etc. can be used.

Other plasticizers, fillers, stabilizers, colorants and the like can be added as required.

To carry out the present invention, a predetermined amount of a polyol, a catalyst, a foaming agent, a foam stabilizer, and a flame retardant and other auxiliaries is mixed to obtain a resin liquid.

Using a polyurethane foaming machine, the resin liquid and the polyisocyanate are continuously and rapidly mixed at a constant ratio. The resulting rigid polyurethane foam stock solution is poured into voids or molds. At this time, the flow rate ratio between the resin liquid and the polyisocyanate is adjusted so that the equivalent ratio between the organic polyisocyanate and the active hydrogen-containing compound is 0.8 to 3.0. The rigid polyurethane foam foams and hardens within a few minutes after injection.

(Example) Hereinafter, the present invention will be specifically described with reference to examples.

The raw materials used in the examples are as follows. Moreover, a part shows a weight part.

Polyether A; a polyol having a hydroxyl value of 400 mgKOH / g obtained by addition-polymerizing propylene oxide to sucrose.

-Polyether B; a polyol having a hydroxyl value of 400 mgKOH / g obtained by addition-polymerizing propylene oxide to tolylenediamine.

Polyisocyanate C; 3,2% by weight of 4,2'-diphenylmethane diisocyanate, 43.4% by weight of 4,4'-diphenylmethane diisocyanate, 53.6% by weight of polynuclear body, and a crude diphenylmethane diisocyanate having an NCO group concentration of 30.8% by weight and a viscosity of 170 cps / 25 ° C. .

Polyisocyanate D; crude diphenylmethane diisocyanate containing 10% by weight of 4,2'-diphenylmethane diisocyanate, 47.1% by weight of 4,4'-diphenylmethane diisocyanate and 42.9% by weight of NCO group concentration of 31.3% by weight and viscosity of 81 cps / 25 ° C. .

Polyisocyanate E; 4,2'-diphenylmethane diisocyanate 20% by weight, 4,4'-diphenylmethane diisocyanate 47.8% by weight, NCO group concentration 31.9% by weight, including polynuclear 33.2% by weight, viscosity 44 cps / 25 ° C.
Of crude diphenylmethane diisocyanate, foam stabilizer, L-5421, catalyst, TMHD and PMDETA, foaming agent, trichloromonofluoromethane (F-11) Example 1 60 parts of polyol A and 40 parts of polyol B were uniformly mixed.

Table 1 shows the results obtained by mixing 100 parts of this polyol mixture with polyisocyanates C, D and E100 and measuring the time until the mixture became transparent.

That is, 4,2 'in crude diphenylmethane diisocyanate
-It is clear that as the content of diphenylmethane diisocyanate increases, the compatibility with the polyol increases, thus shortening the clearing time with the progress of the reaction.

Example 2 A resin solution having the composition shown in Table 2 was prepared, and this was rapidly mixed with polyisocyanate C, D, or E, respectively, and the size 40
Immediately poured into 0x400x50 mm vertical test aluminum panels.

The injection amount was adjusted so as to leave an unfilled portion of 10 to 20% on the upper portion after the completion of foaming.

After heating the panel to 60 ° C. for 10 minutes, the cured rigid foam was removed. 1 for expanded height of rigid foam
It was set to 00%, and the ratio between the height of the generated share line and the height of the foam was measured. In addition, the generation state of voids was observed.

As is clear from Table 2, as the content of 4,2'-diphenylmethane diisocyanate increases, the position of the shear line moves upward. Therefore, when it is completely filled, the shear line collides with the wall surface and tends to collapse and disappear. Also, the occurrence of voids is reduced.

Example 3 Using a high-pressure foaming machine, the flow ratio of the resin liquid and the polyisocyanate was adjusted so as to match the blending amount shown in Table 2, and the mixture was poured into the outer box of a large refrigerator. As a result of disassembling the outer box after leaving it for several days and examining it, some voids and share lines were found in the prescriptions of Table 2 and No. 1, but this was confirmed in the prescriptions of No. 2 and No. 3. I couldn't do it.

(Effect of the invention) By carrying out the present invention, the rate of increase in viscosity becomes slower than the foaming rate of the stock solution, and the compatibility between polyisocyanate and polyol increases, so that voids and shear lines are generated in the rigid polyurethane foam. A homogeneous foam can be obtained.

Claims (1)

[Claims] 1. A polyisocyanate, a polyol, a catalyst,
A method for producing a rigid polyurethane foam by reacting a foam stabilizer and optionally other additives, characterized in that crude diphenylmethane diisocyanate containing 5 to 50% by weight of 4,2'-diphenylmethane diisocyanate is used as polyisocyanate. Method for producing rigid polyurethane foam.