JPS6057456B2 - Manufacturing method and device for resin foam - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to the production of low density freestanding foams of cured urea formaldehyde resin materials.

Foams of this type can be used, for example, in the building industry for thermal insulation purposes. In this specification, the term low density is 20
It is used to mean a dry density of 20k91d or less in the absence of any inert filler, corresponding to a resin solids content of 20k91d or less.

The foam is formed by forming a wet foam consisting of an intimate mixture of a resin and a curing agent for the resin, each initially in an aqueous solution. This wet foam can, for example, be injected into the cavity wall and allowed to cure and dry in situ. While conventional low density urea formaldehyde resin foams have a significant degree of drying shrinkage, it is an object of the present invention to provide a method and apparatus for producing cured urea formaldehyde resin foams having relatively low drying shrinkage. This is one purpose of the invention. As used herein, the term low shrinkage means a shrinkage in volume of 20% or less based on a comparison of the air dry volume and the initial wet volume as delivered by the foam generator. is used. In accordance with the present invention, the cured urea formaldehyde resin foam having a drying shrinkage of 20% or less by volume is such that the wet foam as formed has a drying shrinkage of at least 3% by weight.
It is manufactured by a process that includes forming a homogeneous wet foam from an aqueous resin solution and an aqueous solution of a curing agent for the resin to have a total reactive resin solids content of 5%.

By using a solids content of at least 35% by weight in the wet foam, and thus only 65% water content, conventional foams with water contents of 70% and above are typical. It was found that the drying shrinkage could be reduced significantly more than that of 5.

Conventional foams are manufactured by a process that includes a preparatory step in which a viscous raw resin solution is significantly diluted with water, typically at a volume ratio of at least 1:1. This step has previously been considered essential to ensure proper subsequent mixing with the foamed curing agent solution. In reality, it is further diluted by mixing with the curing agent solution. Generally, a resin to hardener solution ratio within the range of 1:1 to 3:2 is used to obtain the desired final dry density of 20k91d or less. The above products are wet foams containing no more than 20% or at most 30% solids. For purposes of this invention, wet foam is defined as forming a very low density foam from an aqueous solution of a curing agent for the resin, and then combining a relatively undiluted resin solution with this foam. Preferably, they are produced by mixing.

The term "very low density" refers to the fact that dry foams of a desired density of 20k91d or less can be made by prior art methods of making relatively dilute resin solutions, but which are further diluted with hardener solutions. It is used to mean that the curing agent foam density is lower than that normally used in hardener foams. The lower the density of the hardener foam, the lower the concentration of resin mixed with this foam, provided that the final dry foam meets a density level of 20K91 or less in the absence of inert fillers. It can be further concentrated.

Although it is usually very convenient to foam the hardener solution, the present invention may also use the reverse route of mixing a very low density foam of the resin solution with the unfoamed hardener solution. .

[Very low density] has the same meaning as given above with respect to hardener foams. However, for practical purposes, it is usually easier to foam hardener solutions (which usually contain surfactants) than resin solutions, which are viscous, especially when relatively undiluted. Due to the adhesive nature of the resin, considerable difficulty is experienced in mixing the resin with the foamed curing agent solution to obtain a homogeneous wet foam. To overcome this difficulty, the mixing device must be carefully designed and it is necessary to use a mechanical mixing device, such as a power-driven impeller, downstream of the mixing zone. Accordingly, the method of the present invention includes the step of mechanically agitating the initial mixture of foam and solution in order to intimately mix the resin and curing agent to form a homogeneous wet foam. It is preferable. To achieve the very low desired density of the curing agent or resin foam, the solution may be passed through a longer than normal foaming column filled with beads, or a conventionally sized normal sized foam. columns may be used to reduce the column throughput to provide a low density foam. In this specification, "longer than normal"
The term is used for foaming columns of the type used in conventional foam production. Conventional columns of many different sizes and shapes have been used in the production of foams, and optimal operation of any column is achieved by experiment and/or experience. The surfactant content of the solution can also be varied. Many variations in column and surfactant content are possible. However, the maximum benefit in throughput and extremely low foam density compared to conventional foam production is that for a given common column size, an inert material such as a woven or knitted fabric of stainless steel wire It has been found that this can be achieved by replacing the beads with a network structure. Reticulated structures such as those described above present the problem of creating a significant amount of unfoamed or partially foamed liquid process at the beginning of the foaming process. This degree of unfoamed liquid carryover may actually continue throughout the foaming operation. According to yet another aspect of the invention, an apparatus for producing a cured urea-formaldehyde resin foam having a drying shrinkage of less than 20% by volume comprises an upstream material comprised of an inert individual particulate material. and a downstream section constituted by an inert reticulated structure.

"Upstream" and "downstream" refer to the direction of flow of the solution to be foamed within the column. A particularly preferred inert network is, for example, a stainless steel copper wire knitted fabric of the type sold under the trademark "Nitsutomeshi". The material consisting of inert individual particles may be glass marbles. The relative sizes of the two areas mentioned above can vary over a considerable range for any given column size, but in practice areas of approximately the same size (i.e. length) may be satisfactory. It is something. Preferably, the apparatus further includes a mechanical mixing device downstream of the foaming column.

The invention also includes a cured urea formaldehyde resin foam having a drying shrinkage by volume of 20% or less when made by the method or apparatus according to the invention.

The foams are particularly useful for cavity wall insulation because they have significantly lower drying shrinkage than conventional foams. The resin foam thus shrinks and detaches from the walls of the cavity considerably less than conventional foams. Also, due to its low water content, the use of this resin foam as insulation in attic storage significantly reduces the risk of water penetration through the plaster or plasterboard ceiling. The risk of water penetration and resulting ceiling staining has now discouraged the use of urea formaldehyde resin foam as an insulation material for attic storage bays. The method of the invention will now be explained in detail with reference to the accompanying drawings. In the accompanying drawings, a tubular column 1 has an inlet 2 and an outlet 3. Two areas A (5
B is filled with glass marbles each having an average diameter of 6 mm and a large amount of knitted stainless steel wire. In this example, both sections have a length of 1807 wt and column diameters of 45 ordinal. The outlet 3 is connected by a short tube to a mechanical mixer 4, in which a resin solution delivery nozzle 5 is arranged so that resin can be forced into the tube from a dispensing vibe 6. Nozzle 5 is arranged to direct the flow of resin toward mixer 4 . The mixer 4 includes a rotatable impeller 7 which is formed of a nearly cylindrical chamber with a diameter of 65 TWL and has a large number of small holes. An air motor 8 is provided to drive the impeller from outside the chamber. The outlet vibrator 9 extends tangentially to the exterior of the room and constitutes a tail vibrator for supplying wet foam wherever it is needed. EXAMPLE In a particular operation, a curing agent solution containing 1.4% surfactant by weight was fed into inlet 2 at a rate of 2 liters per minute.

Inlet 2 is also supplied with air at 40 KNI to produce a very low density initial foam at outlet 3. The operation was carried out at room temperature (25°C). This "extremely low density" is assessed by comparison to conventional foam production runs described below. 76% reactive resin solids by weight
% aqueous resin solution was fed through the vibrator 6 at a rate of 2112 liters per minute and mixed with the foam in the short tube and mixer 4. The impeller is 900r.
p. m. I rotated it. In this example, the resin has a molar ratio of 1:
1 to 1:1.6 urea/formaldehyde resin (“
゜BEETLE゛BU7OO), and the curing agent is
C'BEETLE, a phosphoric acid aqueous solution containing 1.4% Na dodecylbenzenesulfonate as an anionic surfactant
It was ゛FHlOO). 6'BEETLE'' is a registered trademark of Briteishi Industrial Plastics Co., Ltd.

The homogeneous wet foam discharged from the tail vibe 9 had a total reactive resin solids content of 47% and a water content of 53%.

After curing and drying, the foam has a shrinkage of 15% or less by volume;
It had a final dry density of 14k91d. As a comparison example, 6Trr! A conventional foam was produced using a column filled only with n glass marbles.

Mixer 4 was not necessary to produce a homogeneous foam. The resin solution was supplied at a rate of 3 liters per minute,
% reactive resin total solids. The curing agent solution was the same as in the example above and the same flow rates were used.
However, the density of the curative foam produced was much greater than that produced in the Examples. The homogeneous wet foam discharged from the tail vibrator contains 20% resin solids and 80% resin solids.
It contained % of water. The final dry density of the cured and dried foam was 14k91d, but the dry volume was 2.
It shrunk by more than 4%. In the Examples and Comparative Examples, curing drying was carried out under similar environmental conditions in terms of temperature and relative humidity.

[Brief explanation of drawings]

The accompanying drawing is a side view in section through a foam generator according to the invention. 1...Tubular column, 2...Inlet, 3...Outlet, A...Glass marble area, B
... Stainless steel wire knitted fabric, 4 ... Mechanical mixer, 5 ... Feeding nozzle, 6 ...
Supply vibe, 7... Impeller, 8... Air motor, 9... Outlet vibe.

Claims (1)

[Scope of Claims] 1. A method for producing a cured urea formaldehyde resin foam exhibiting a drying shrinkage of 20% or less by volume, comprising: a mixture of an aqueous solution of said resin and an aqueous solution of a curing agent for said resin; In forming a homogeneous wet foam, the total reactive resin solids content in the wet foam is at least 3 by weight.
A method for producing a urea-formaldehyde resin foam, the method comprising adjusting the content to 5%. 2. The method of claim 1, wherein the formation of the wet foam is carried out by intimate mixing of an initial low density wet foam formed from the curing agent solution and the undiluted resin solution. 3. The method of claim 1, wherein the formation of the wet foam is carried out by intimate mixing of an initial low density wet foam formed from the undiluted resin solution and the curing agent solution. . 4. The method according to claim 2 or 3, wherein the dense mixing is performed by mechanical stirring. 5. The method of claim 2 or 3, wherein the formation of the initial low density wet foam is carried out by passing the solution through a foaming column packed with spherical beads. 6. The method of claim 2 or claim 3, wherein the formation of the initial low density wet foam in a column is carried out by reducing column throughput to provide a low density foam. 7. The method of claim 2 or 3, wherein the formation of the initial low density wet foam is carried out by passing the solution through a foaming column packed with an inert network structure. 8. An apparatus for producing a cured urea formaldehyde resin foam exhibiting a drying shrinkage of 20% or less by volume from an aqueous solution of urea formaldehyde resin and an aqueous curing agent solution for the resin, having an inlet 2 and an outlet 3. Column 1, which column has between the inlet and the outlet an upstream section A made up of an inert individual particulate material and a downstream section B made up of an inert network structure. A device comprising a foam column. 9. The inert network is a woven stainless steel wire. An apparatus according to claim 9. 10 Claim 9, wherein the individual inert particles are glass beads.
Apparatus described in section. 11. The apparatus of claim 9, wherein the upstream and downstream sections of the column are approximately equal in size. 12. The apparatus of claim 9 further comprising a mechanical mixing device downstream of the foaming column.