JPH0830316B2 - Impregnated grade paper - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a veneer, such as a high pressure veneer. More specifically, the present invention relates to a sheet of resin-impregnated paper, that is, an impregnated-grade paper used as a core material for decorative boards when impregnated with a synthetic resin. Even more particularly, the invention relates to the combined use of titanium dioxide and certain silica fillers in such resin impregnated paper sheets.

Veneer has been commercially produced for many years. Generally, this type of decorative board is composed of a plurality of so-called cores or body sheets made of a fibrous cellulosic material (usually kraft paper) impregnated with a synthetic resin composition, an impregnated decorative coloring or printing sheet placed on the plurality of core sheets. , And the impregnated surface or overlay sheet for protecting the dip printing color or colored sheet has been made by fixing under heat and pressure. Such veneers have been widely adopted in many applications, such as wall structures, tables and desktops, counter decks, furniture and the like.

Although the core sheet is cheaper than the printing or overlay sheet, it is an important cost factor due to the plurality of core sheets used for the decorative board. Typically 30
130 pounds communication (3000ft ²⁾ 3~9 sheets of paper of the core sheet is used in making a decorative plate. The main inorganic oxide filler used in impregnated paper sheets is titanium dioxide.
Titanium dioxide is particularly useful as a filler due to its high refractive index and high optical scattering power due to its uniform fine particle size. Titanium dioxide is relatively expensive compared to other fillers used in the paper industry, but due to its optical properties, the opacities of impregnated sheets (and veneers made from it) that cannot be obtained with other fillers ( opacity) and gloss (brigh
tness). Lowers the cost of the core sheet by reducing the amount of titanium dioxide filler contained in the impregnated paper sheet without compromising opalescence and gloss, making more impregnated paper sheet even when titanium dioxide is thin It will be possible.

It has now been found that about 5 to about 40% by weight of titanium dioxide used as a filler in impregnated grade paper can be replaced by a particular amorphous precipitated silica without loss of opalescence and gloss. While such BET surface area of the silica can be varied within a wide range of made variable, generally from about 25 to about 200 meters ² / g, especially about 40~120m ² / g, especially about 40
12m ² / g, for example from about 50 to about 100 m ² / g. The pH of such silicas is about 6 to about 9.5, but is preferably about neutral, ie, in the range of about 6.5 to 7.5. Median agglomerate particlen
size) is less than 30 micrometers, preferably 3-10 micrometers, for example about 3-5 micrometers.

In general, the polymerization of monomer silica molecules proceeds via dimers, cyclics, etc., eventually forming independent silica particles. The silica particles can be aggregated in large numbers to form larger aggregate units that can be measured as a single entity. The aggregate units thus formed in the amorphous precipitated silica are referred to herein as "aggregate particles".

On the other hand, the “median” is the observation value that is in the middle when the observation values “x ₁ , x ₂ , ..., X _n ” are arranged in order of size.

Therefore, in the present specification, the “median value of the particle size of aggregates” means the measurement value in the middle when the particle sizes of aggregates of amorphous precipitated silica are sequentially measured and arranged in order of size. To do. These measurements are
Counter particle size analyzer (Coulter Counter Partic)
le Size Analyzer). Amorphous precipitated silica is added, coformed or coprecipitated calcium compounds, such as calcium oxide, or calcium salts, such as calcium silicate, calcium chloride, except for calcium taken up from water used in the manufacturing process. Alternatively, it does not substantially contain calcium sulfate. The amount of such calcium compounds contained in the amorphous precipitated silica is generally less than 1% by weight (calculated as calcium oxide), eg 0.75% by weight.
It is the following.

A grade of amorphous hydrated precipitated silica
It has been proposed to be used as a filler in paper types other than impregnated paper sheets, for example to replace part of the titanium dioxide pigment used or to enhance inexpensive fillers such as clay. There is. The grade of hydrated silica proposed for such use is about
It consists essentially of 78 percent silica and 5 to 7 weight percent calcium dioxide. This silica has an alkaline surface area of about 40 m ² / g with a pH of about 10. Such silicas have not yet been used or proposed for use in the manufacture of impregnated grade paper.

DETAILED DESCRIPTION OF THE INVENTION The amorphous precipitated silica used to replace some of the titanium dioxide filler contained in impregnated grade paper is essentially a neutral, finely ground white powder. The median particle size of the silica agglomerates is less than about 30 micrometers, preferably about 3 to 10 micrometers, for example 3 to.
It is 5 micrometers. The BET surface area of this silica is about 2
5 to about 200 m ² / g, especially about 40 to about 120 m ² / g. Preferably, this surface area is about 50 to about 100 m ² / g. More preferably, this surface area is 60-90 m ² / g. The silica is a hydrated, relatively pure silica, ie, about 88-90% by weight silica, which is a compound of an alcal earth metal (eg calcium) (eg oxides and salts), eg calcium oxide, silicic acid. It is substantially free of calcium, such as calcium, calcium chloride and calcium sulfate.

The amount of adsorbed water present in the hydrated amorphous precipitated silica is generally about 3 to about 7% by weight, for example about 5% by weight. The amount of adsorbed water depends somewhat on the relative humidity of the prevailing.
Adsorbed moisture is the water removed from silica by heating it in an oven at 105 ° C. for 24 hours under atmospheric pressure. The silica also contains bound water in an amount of about 2 to about 6% by weight. Bound water is the temperature at which silica is fired, for example 100 ° C.
Water that is further removed by heating at ~ 1200 ° C.

The preferred silica is essentially neutral. 5% by weight
The pH of the aqueous pigment slurry of about 6-9.5 is preferably in the range of about 6.5-7.5, for example about 7.

The above-mentioned amorphous precipitated hydrated silica is obtained by neutralizing an aqueous alkali metal silicate solution with an inorganic acid such as carbonic acid, hydrochloric acid or sulfuric acid. Soluble alkali metal silicates may be either commercial or industrial grades of alkali metal silicates such as sodium silicate, potassium silicate or lithium silicate. Sodium silicate is commercially available, readily available, is the cheapest of the aforementioned silicates, and is therefore the alkali metal silicate of choice. The alkali metal silicate is represented by the molecular formula M ₂ O (SiO ₂ ) _x . In the formula, M is an alkali metal and x is a number from 1 to 5. More generally, x is a number from 3.0 to 3.4, such as 2 to 4, for example 3.2 or 3.3. Typically about 1: 3.
Sodium silicate with a Na ₂ O: SiO ₂ ratio of 0 to 1: 3.4, for example 1: 3.2 to 1: 3.3, is used to prepare the aqueous soluble silicate solution. The concentration of the aqueous sodium silicate reactant solution can vary widely. For example, about 18.75 g / l to about 90 g /
A sodium silicate solution with a Na ₂ O concentration of 1 is used.

Sulfuric acid is preferred for use as the acidifying agent. An acidifying agent, such as sulfuric acid, is slowly added to the aqueous sodium silicate solution to neutralize the alkali content of the solution and precipitate the silica.
The dry silica product is essentially neutral with
Sufficient acidifying agent is used for neutralization to exhibit pH. It is typical to add the acidifying agent over a period of about 1 to 4 hours, such as 2 to 4 hours. The temperature at which the alkali metal silicate is acidified is about 175 ° F. (79 ° C) to 210 ° F. (99 ° C), more typically 180 ° F. (82 ° C) to 190 ° F. 88 ° C). Agitation of the aqueous reaction medium at high speeds reduces the amount of gel formed during the precipitation reaction, although high shear agitators are preferred for such agitation.

The precipitated silica is recovered from the suspension aqueous reaction medium by a conventional solid-liquid separation means, such as a filter press, a drum filter, a centrifuge, etc., and washed with water to remove alkali metal residues such as sodium and inorganic salts, Dry and grind to the median particle size of the agglomerates described above. Typically, the recovered precipitated silica has an alkali metal salt (eg, sodium sulfate) content of less than about 2% by weight, such as 1.
It is washed so as to be reduced to 5% by weight or less, for example, 0.8 to 1.2% by weight. Drying of the washed silica may be accomplished by any suitable drying means, such as a tumble or drum dryer, a spray dryer, or a compartment dryer. Depending on the dry type used, dry silica is ground if necessary. For example, fluid energy mill, vertical mill, hammer mill, etc. are carried out, and if necessary, the median particle size of the agglomerates is divided into particles having a median value of 30 microns or less, preferably 10 microns or less. To be Vertical mills are preferred.

In a typical method for producing the amorphous precipitated silicas described herein, water is charged to a suitable reaction vessel and the desired initial settling temperature with steam, for example from about 182 ° F. (83 ° C) to about 186 ° F. 86
(° C). Then an aqueous solution of sodium silicate,
Add to the heated water until the concentration of sodium silicate is about 40 g / l Na ₂ O. Then, stirring in the reaction vessel is started, and concentrated sulfuric acid is gradually added to the sodium silicate aqueous solution over about 3 hours. The pH of the reaction slurry was adjusted to about 4 by adding sulfuric acid.
Continue until you reach. The pH of the aqueous reaction slurry is measured for a short period of time, for example 15-45 minutes, to make sure that the pH of the slurry is stable and does not shift to the higher direction, ie, more alkaline. The produced precipitated silica is separated from the aqueous reaction slurry by, for example, a drum filter, spray-dried, and then subjected to a Coulter counter (Coulter conute).
r) Mill vertically until the median agglomerate particle size is less than 5 micrometers as measured by a particle size analyzer.

The amount of essentially neutral amorphous precipitated hydrated silica that replaces the titanium dioxide filler in the impregnated grade paper may be from about 5 to about 40 wt% based on titanium dioxide. More typically, the amount of silica used may be from about 10 to about 25% by weight of the titanium dioxide filler. Only this amount of amorphous precipitated silica was used as an alternative / extender for titanium dioxide, and the opalescence value of the paper (and veneer) substantially equivalent to that obtained using titanium dioxide alone. Gloss value is obtained. Further, the laminate should not yellow when stuck under heat and pressure. Yellowing may be evaluated by testing the laminate with a Fadeometer.

The titanium dioxide used as a filler in impregnated grade paper may be in the anatase or rutile crystalline form. Rutile titanium dioxide is preferred for resin impregnated grade paper.

The core sheet material used in the impregnated grade paper may be pulp fibers obtained from conventional papermaking processes and softwood, hardwood or mixtures thereof. The pulp may be acid (sulfite), alkaline (soda or kraft), neutral and groundwood pulp made. The pulp may be bleached by performing a chlorine, hypochlorite, hydrogen peroxide, or hydrosulfite bleaching step, or may be unbleached. Typically, the impregnated grade paper is about 30-130 pounds / ream weight (3000 ft ² ), for example 40-12.
Made from bleached kraft paper with 0 pounds / ream weight (3000 ft ² ). Paper fillers, ie titanium dioxide, and the alternatives / extender silicas mentioned herein may be added at any point during the wet end of the papermaking system, for example in a bed box or beating or refining operations.

In the production of a decorative board using impregnated grade paper, the core sheet is impregnated with the resin composition for lamination. The resin composition is typically a phenol-formaldehyde resin, although other resins and resin combinations may be used. For example, U.S. Pat. Nos. 3,220,916, 3,218,225 and 3,589,974 describe impregnating craft core sheets with conventional phenolic resins in making high pressure veneer. U.S. Pat.Nos. 3,938,907 and 3,975,572 disclose the use of mixtures of melamine-formaldehyde and acrylic resins.
4,473,613 describes thermosetting formulations of phenol-formaldehyde resins, crosslinked acrylic resins and optional melamine-formaldehyde resin mixtures.

 A thermosetting fiber used to impregnate core sheets.
The resin for laminating the formaldehyde and phenol is phenol and resin.
Lumaldehyde was added at a molar ratio of about 1: 1 to about 1: 2.5, respectively.
To prepare. These resins are liquid and water-soluble resins.
Is. Melamine-formaldehyde resin and melamine
The formaldehyde molar ratio is about 1: 1 to about 1: 3, respectively.
A water soluble resin prepared according to steps well known to those skilled in the art.
It Other laminating resins that may be used are amines,
Ril, epoxy, polyester, silicone and diallyl
Phthalate resins, which are processes known to those skilled in the art.
Is prepared by. For example, acrylic resin is a known
Ril copolymerization reaction, that is, solution polymerization, bulk polymerization, emulsion polymerization
According to any suitable catalyst, eg free radical
Prepared using a generator. This acrylic polymer is
Well known to traders, such as Rohm and Her
Commercially available from Rohm and Haas Company
Plex HA-12 (Rhoplex HA-12) and TR-934
It is a resin. These products are made of acrylic resin, for example
Aqueous milk of copolymer of ethyl phosphate and metal methacrylate
It is a suspension.

The resin composition for synthetic lamination is used by impregnating a core sheet, for example, a kraft sheet, with an immersion and squeezing treatment apparatus or other known impregnation equipment, for example, dipping and spraying, an aqueous solution of this resin to impregnate the core sheet with the resin. Is also good. The resin is impregnated into the sheet in an amount of about 15 to about 55% by weight, preferably about 20 to about 40% by weight, based on the weight of the paper. Various additives may be added to the aqueous resin formulation. Additives such as urea, strippers, defoamers, catalysts, wet strength agents and crosslinkers fall into the category of useful additives.

The veneer typically consists essentially of three layers: a core amount, a printing layer and a surface layer. The core layer comprises a lower or support layer to which other layers adhere. In conventional high pressure laminate manufacturing, the core layer is composed of multiple cellulosic sheets,
For example, it is made of resin-impregnated kraft paper. The number of sheets used in the core layer may be from about 3 to about 9, for example 5 to 8. A printing layer is coated on the core layer. The printed layer is generally an α-cellulose colored paper containing a print, design or design impregnated with a melamine-formaldehyde resin. Printing is typically done before impregnation with high speed gravure. The so-called surface layer or overlay sheet is typically high quality α-cellulose impregnated with a melamine-formaldehyde resin. This layer allows the printed sheet to be exposed to external factors such as wear and tear, chemicals, burns,
Protect from such things as spillage.

In the production of a decorative plate, the core layer, the printing layer and the surface layer are laminated in the order in which they are laminated, and the resulting bundle of sheets is sandwiched between polished steel plates to cure the laminating resin impregnating each layer. Apply pressure and temperature for a sufficient amount of time. The temperature is typically about 120 ° C to 250 ° C. The veneer may be made at both high and low pressure. High pressure veneer is typically about 80
0 to about 1600 lb / in ² (psi) pressure (5.5 to 11 MPa),
For example, it is formed at 1000 psi (6.9 MPa). A soft decorative board is at a low pressure, for example, 5.5 MPa or less, for example, 175 to 225 (1.2 to 1.6
Made at a pressure of MPa).

Veneers, especially high pressure laminates, are useful in the manufacture of furniture, kitchen counter decks, table tops, store furniture, wall panels, bulkheads, doors, bathroom and kitchen workpiece surfaces and wallpapers.

This will be described in more detail in the following examples of the invention, but this is intended only as an illustration, as many modifications and variations will be apparent to those skilled in the art.

Example 1 Canadian standard free of 475 +/- 25 milliliters (ml)
Ness (Canadian Standard Freeness) (CSF)
2964.5 grams (g) of 50/50 hardwood / softwood bleached craft
26.7g of rutile titanium dioxide (Dupon
ont) R-794) and 33.7 g slurry of deionized water.
did. 1.05 g of paper alum was added to this mixture
(Equivalent to about 10lbs dry alum / ton). Product formulation
Is diluted with deionized water to a consistency of about 0.03% and a small amount of aluminum
Sodium acid is added to the resulting slurry to bring the pH to 6.3.
I adjusted. 41 lbs / 3000ft²A series with a base weight of
8 inch x 8 inch (20.3 cm x 20.3 cm) hand sheet
(Handsheet) from this slurry to Nobel and Wood
It was made by a machine (Nobel and Wood machine). This han
The seat through a felt press.
Dry the sheet with a dryer until the moisture content of the sheet is about 5% by weight.
Was. This sheet is then proofed at 72% (22 ° C) and 50% temperature
It was placed in a relative humidity chamber. Gloss and opalescence of typical sheets
And% ash were measured. Gloss and opalescence are
ISO STANDARD Nos. 2470 and 2471
El Refo using the law (Elrepho ) Is used to measure
Was.

 Hand sheet is 2 inches (5.1 cm) x 8 inches (20.3c
m) cut into strips, each strip American
・ Cyanamide Company (American Cyanamid Compan
y) Commercially available melamine-formaldehyde resin simel
(Cymel ) 412) was soaked in 50% aqueous solution for 45 seconds. Each
Take the trip out of the resin solution and use it for stainless steel.
Excess resin was removed by pulling on a cheer bar. This
Place the trip in an oven at 105-110 ° C for 5 minutes to load the resin
It was polymerized and the moisture was removed. This resin impregnated strip
Was then placed in a constant relative humidity chamber. Resin impregnated strip
Opalescence, luster and el refo It was measured with a meter.

 The results obtained are shown in Table I.

Example 2 The procedure of Example 1 was repeated except that 2967.9 g pulp, 24.01 g titanium dioxide (TiO ₂ ) and 2.7 g amorphous precipitated silica (SiO ₂ ) were used. The amount of silica used replaced about 10% of titanium dioxide. The silica had a BET surface area of about 71 m ² / g, a pH of 6.8 (5% slurry in water), a median aggregate particle size of 4.3 microns, and contained about 0.48% sodium sulfate ( X
Line test). The results are shown in Table I.

Example 3 The procedure of Example 1 was followed except that 2954.7 g of pulp, 21.34 g of titanium dioxide and 5.4 g of Example 2 of silica were used. The amount of this silica is about 20 of titanium dioxide.
It was a substitute for%. The results are shown in Table I.

The results in Table I show that as much as 20% of titanium dioxide can be replaced by the essentially neutral silica described without compromising the gloss and opalescence of the paper. Ash values of various sheets are also constant around 23.0-23.5%.

Example 4 Using 2948.8 g pulp and 26.8 g titanium dioxide
The procedure of Example 1 was followed. Further 1.34 g of simmer Four
12 Weld the resin solution on the wet end of the papermaking machine (for composition
0.5%) as a wet strength additive. Data
Shown in Table II.

Example 5 24.2 g titanium dioxide in 2948.8 g pulp, 2.7 g run
Silica from Example 2 and 1.34 g shimel Using 412 resin solution
Was performed according to the method of Example 4. The amount of this silica is
It replaced about 10% of titanium dioxide. data
Are shown in Table II.

Example 6 2948.8 g pulp, 21.4 g titanium dioxide and 5.4 g fruit
Example 2 silica and 1.34 g shimel 412 resin aqueous solution
The method of Example 4 was followed. The amount of this silica is
It replaced about 20% of titanium. Data in Table II
Shown in.

The data in Table II shows that 20% of titanium dioxide is 0.5%.
It shows that the essentially neutral silica described in the impregnated sheet containing wt% wet strength additive can be substituted.

Although the method of the present invention has been described with respect to particular details of certain embodiments, such details are intended to limit the scope of the invention, except where it is within the scope of the appended claims. Not a thing.

 ─────────────────────────────────────────────────── --Continued from the front page (56) Reference JP-A-56-9499 (JP, A) JP-A-52-115831 (JP, A) JP-B-56-45392 (JP, B2) US Patent 3737371 (US) , A)

Claims (14)

[Claims] 1. A resin-impregnated paper sheet containing titanium dioxide as a filler and 5-40% by weight of amorphous precipitated silica based on said titanium dioxide, said amorphous precipitated silica being BE.
Resin surface impregnation characterized by having a T surface area of 25 to 200 m ^{2 /} g, a pH of ^{6 to} 9.5 and a median particle size of 30 micrometers or less, and containing 1% by weight or less (calcium oxide equivalent) of calcium. Paper sheet. 2. Amorphous precipitated silica having a BET surface area of 40-120 m ² / g, a pH in the range of 6.5-7.5 and a median particle size of the agglomerates of 3-10 micrometers. of_
Paper sheet. 3. The content of silica is 10 to 10 with respect to titanium dioxide.
The paper sheet according to claim 2, which is 25% by weight. 4. The paper sheet of claim 3 wherein the amorphous precipitated silica has a BET surface area of 50 to 100 m ² / g and a median particle size of agglomerates of 3 to 5 micrometers. 5. The paper sheet according to claim 4, wherein the titanium dioxide is in the rutile crystal form. 6. A paper sheet according to claim 5, wherein the paper is made from bleached kraft paper. 7. A resin-impregnated paper sheet of bleached kraft paper containing rutile titanium dioxide as a filler and 10 to 25% by weight of amorphous precipitated silica based on said titanium dioxide. Silica has a BET surface area of 50-100 m ² / g, pH 6.
A resin-impregnated paper sheet of bleached kraft paper, which has a median particle size of 5 to 7.5 and an aggregate particle size of 3 to 5 micrometers or less, and contains 1% by weight or less of calcium (calcium oxide equivalent). 8. A resin-impregnated paper sheet obtained by impregnating the paper sheet according to claim 7 with a synthetic resin composition. 9. The resin-impregnated paper sheet according to claim 8, wherein the synthetic resin composition is selected from the group consisting of phenol-formaldehyde resin, melamine-formaldehyde resin and polyester resin. 10. A decorative board, wherein at least one sheet of the core is a titanium dioxide-filled impregnated paper sheet impregnated with a synthetic laminating resin composition, wherein the impregnated paper sheet comprises 5 to 40% by weight of the titanium dioxide based on non-concentration. Amorphous precipitated silica containing BET surface area 25-200 m ² / g,
A decorative board having a pH of 6.5 to 9.5 and a median particle size of 30 micrometers or less and containing 1% by weight or less of calcium (calcium oxide equivalent). 11. An impregnated paper sheet is used for titanium dioxide in an amount of 10.
-25% by weight of amorphous precipitated silica, said amorphous precipitated silica having a BET surface area of 50-100 m ² / g, a pH of 6.5-7.5 and a pH of 3
11. The veneer according to claim 10 having a median particle size of agglomerates of -10 micrometer. 12. The impregnated paper sheet is made from bleached kraft paper, silica having a median particle size of agglomerates of 3 to 5 micrometers, and titanium dioxide in the rutile crystalline form. Veneer as described. 13. The decorative board according to claim 12, wherein the silica has a BET surface area of 60 to 90 m ² / g. 14. The decorative board according to claim 12, wherein the impregnated paper is impregnated with a synthetic laminating resin composition selected from the group consisting of phenol-formaldehyde resin, melamine-formaldehyde resin and polyester resin.