DE1696242A1 - Paper web for use as a laminate top layer - Google Patents

Description

Ma 542

Plastics Manufacturing Company, Dallas (Texas) / USA

Paper web for use as a laminate top layer

The invention relates to the production of fast-curing laminates with high Flee kenunsenslich- ^ and excellent (gloss durability.

Melamine-formaldehyde resins are used for lamination operations Used extensively, in particular for the production of top layers that are pleasing to the laminate and give a permanent surface.

The melamine formaldehyde resin which is used for manufacturing a sheet for a laminating process, must be in the form of an aqueous solution containing at least twelve 'm Hours remains stable. A bit to be impregnated Melaainformaldehydharz a path for a laminating process usually consists of a rolled-up, i together hanging paper layer which continuously prägniereinrichtung by the import · passes Such _a Imprägniereinriohtung consists in practice mostly from a. Series of containers filled with said aqueous solution of a melamine-formaldehyde reaction product

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The impregnation process takes place either by means of rollers or in such a way that the paper web is pulled directly through the solution. The tanks of the Impregnation devices generally have to be used for a whole working day with the said watery Solution of the melamine-formaldehyde reaction product filled stay; during, this time as well as during a subsequent one During the period of time for cleaning the tanks, the solution mentioned must remain stable; so it is especially allowed no gelation will occur. This explains the above-mentioned requirement that one should be practical Lamination and impregnation purposes a suitable solution. Melamine / formaldehyde reaction product at least ^ wolves Stable and ungelled hours after the solution was made must stay "

To meet this requirement, it was previously necessary Formaldehyde and melamine in a molecular ratio of more than 2: 1 to react »Bine aqueous solution prepared from this reaction product On the one hand it is sufficiently resistant and on the other hand it ensures that one is impregnated with this solution Paper web sufficiently quickly at elevated temperature and the pressure present in conventional lamination processes hardens.

To use an aqueous solution of a reaction product 109883/0286

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formaldehyde and melamine with a molecular ratio of less than 2: 1 an impregnated material web that hardens sufficiently quickly at elevated temperature and pressure to achieve- »said solution would have to contain a relatively large proportion of an acid catalyst. However, this makes the solution unstable, so that it becomes too in the containers of the impregnation device a gelling process comes ...

The invention uses a novel aqueous solution a curing under YJarme Ileaktionspro product of Formaldehyde and melamine in a molecular ratio between 1; 1 and 1.9: 1. This solution is stabilized in such a way that that it can be used in conventional impregnation facilities. One impregnated with this solution When used as a cover layer in a lamination process, the paper web also results in a rapidly hardening laminate significantly improved performance properties.

The invention is based on τοη a paper web as Surface layer in the manufacture of objects using. high sensitivity to staining and excellent Gloss halfability in a hot pressing process> wherein the cellulose fibers of the paper web mil: a hardening Reaction product of formaldehyde and melamine in a Heolekttlarverhäitnia between 1: 1 and 1.9; 1 impregnationx The invention is based on cellulose fibers

109883/0288

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furthermore with a water-soluble, acid-forming sals an amphoteric metal of the class (group) containing aluminum and zinc, impregnated.

The invention "is based on the knowledge that such a salt acts as a latent curing catalyst" when it is in an aqueous solution of a hardenable Res.ktionsproduktes of formaldehyde and melamine in one Molecular ratio between 1: 1 and 1.9 J 1 inserted becomes., The solution thus formed is on the one hand sufficient ■ resistant, so that they can be used in standard waterproofing devices can be used; on the other hand, a paper web impregnated with this solution hardens quickly «, Es wird also found that a laminate having a top layer impregnated with said solution, a Significantly greater resistance to stains and better gloss retention than the previously known Helanrilnforraaldehydlaminate having·

A v / es ent Liehe s field of application of the invention lies in the preparation of the Oberflächenschichten'von of melamine-formaldehyde resins prepared dishes, for example Ellern of "and cups. About 80 $ of the harness produced from melamine formaldehyde resin for domestic use comprises a decor. Typically, the paper web the surface layer forms, printed on its underside with an often multi-colored hub ter.

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In the following pressing process, the impregnated paper web then forms the surface layer on the one side of the subject »This essentially transparent layer reveals the pattern «this is indicated by the arrangement. the bottom of the layer is protected "

However, "dishes provided with a decoration" produced by this method have the disadvantage that the decorative surface produced by the surface lamination has less of its original gloss and is more sensitive to stains and a further loss of gloss during use than a surface of an object that does not have any Surface laning provided iat "In other words," it is possible to decorate a shaped object by lining the surface, but only at the expense of the inherently desirable stain resistance, the initial luster and the luster durability of the surface provided with the pattern The last-mentioned disadvantages, however, are particularly significant because the side provided with the decoration, for example the top of a plate, is precisely that side of tableware which is the main view when the object is used / For this reason nd - / find such a thing with decor 109085/0216

Selienes dishes in. Restaurants and similar establishments, where a much more intensive use of the dishes than takes place in the household, only to a relatively small extent few cases used *

It was now showing. da3 also in this respect through use a surface layer produced according to the invention a substantial improvement is achieved, when used the paper web impregnated according to the invention as a cover layer of the laminate even results for the upper side olne greater sensitivity and a higher stain • Durability than the bottom of the item.

Due to this improvement, dishes of this type provided with a decoration can now also be used in facilities., How Kestaurants »are used in which it was previously not usable for the reasons explained.

Preparation of the stabilized aqueous solution:

The stabilized aqueous solution of the invention can be prepared in such a way that one mole of melamine in an aqueous solution the 1 to 1.9 moles of formaldehyde contains »is dissolved * The concentration of the aqueous of the formaldehyde is chosen so that the addition

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oats - the melamine gives a solution with $ 45 to $ 60 solids. For the calculation of the solids content of the solution is that angenonmen _t formaldehyde for 3 per mole is cleaved off during the reaction, 1 mole of water. Before adding the lielaniin aur formaldehyde solution, a base such as sodium hydroxide or an acid such as formic acid is added to the formaldehyde solution, as far as this is necessary in order to obtain a solution with a pK word between 8 and 9 after adding the melamine and heating to about 93 ° 0 Han then lets the solution run back at atmospheric pressure until toe is added. a drop of the solution in a large one. Water volume at 38 ° C turbidity occurs. The solution is then cooled to room temperature as quickly as possible.

If the molecular ratio used for the reaction is found from formaldehyde to melamine the value 1 «approaches 9» so the advantages achieved according to the invention decrease somewhat » On the other hand, when the molecular ratio approaches 1 ι 1, it becomes more difficult to obtain a pure solution to achieve. The preferred molecular ratio of formaldehyde to melamine according to the invention is approximately between 1.2: 1 and 1 "7 s 1" One produced in the manner explained Solution with a molecular ratio in this preferred range will remain stable for two to four weeks * if no curing catalyst is added vrir'cL

For the production of eggs stabilized according to the invention

109883/0286

BATH ORIGINARY

aqueous solution, a latent curing catalyst is added to the solution prepared in the manner explained above, which consists of a water-soluble, acid-forming aluminum or zinc salt. The amount of this added catalyst depends on the type of catalyst and can be between 0.05 and 2 fo The amount of latent curing catalyst added is usually between 0.1 and 1.0 percent by weight of the solution _β

Any acid-forming catalyst can be used as a latent curing catalyst Find aluminum or zinc salt use, such as e.g. aluminum acetate, aluminum lactate, zinc acetate or the other water-soluble, acid-forming salt of Aluminum or zinc with an organic acid »However, water-soluble salts of or zinc with a strong inorganic acid, such as -aluminium sulphate ^ aluminum chloride ", aluminum nitrate, zinc sulphate, Zinc chloride or zinc nitrate.

The concentration of the aqueous solution according to the invention can be varied within wide limits. All that is required is that it transfers the desired amount of the helajnine formaldehyde reaction product to the paper during the impregnation process. The concentration of the solution is usually between 30 and 70 fa solids.

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Example t:

1 mol of melamine was added to an aqueous solution of 1.5 kol of formaldehyde and heated to 93 ° C. so that a clear solution with a pH between 8 and 9 resulted. The solution was then refluxed at atmospheric pressure until the addition From a drop of the solution to a large volume of water at 38 ° C., turbidity occurred. After rapid cooling to room temperature, the solution thus prepared remained clear for a period of two to four weeks. The concentration of the initial aqueous solution of formaldehyde was chosen so that the final solution had a solids component (calculated in the manner explained) of 53 % ,

The prepared solution was divided into several parts. To one of these parts O _S was used to prepare the erfindungBgeiBäßen solution then added 3 percent by weight aluminum nitrate * The resulting solution had a pH of 7.15 and was able to impregnate paper _"s are used, the produced the top layer of a conventional heat-press process, This solution remained clear for more than seven hours after the addition of aluminum nitrate at 24 ° C. After about ten hours, a light haze developed in the solution at this temperature; after about eighteen hours the solution became cloudy, was

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-10.-but can still be used after about twenty hours.

Another solution according to the invention was made soluble with a further part of the explained starting point by adding made of 0.6 weight percent zinc sulfate, the so formed Solution could be used in the same way as the above-mentioned solution with aluminum nitrate; she had a pH of 7.4 and at the stated temperature of 24 ° G has about the same stability as the solution with Aluminum nitrate.

Another part of the above was used as a control Starting solution a solution by adding 0.6 Weight percent lactic acid heard. The resulting Solution had a pH value of 6.7 and could be used immediately after its preparation (without standing time) Impregnation paper can be used, 'A xinter use Laminate made with this reference solution cured no faster than a laminate made using that of the two aforementioned solutions according to the invention was prepared. A use of the comparison solution in usual waterproofing facilities was not possible there this solution; about five hours after adding the lactic acid began to gel and thus became unusable »

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. - 11 Manufacture of the impregnated paper:

With a solution according to the invention, paper in the usual way to be impregnated, a cohesive Paper web can be supplied from a supply roll for this purpose and, for example, impregnated by means of application varnish or passed directly through a bath of the solution v / earth. Preferably, both possibilities are used one after the other, so that the paper web is initially

is impregnated by means of rollers and then runs through the solution _a

Since dealing with a melamine-formaldehyde reaction product allows very light colors and a high color fastness to be achieved, paper5. that with such a Reaction product is impregnated, often as a top layer used in the manufacture of a laminate.

The paper used for this is usually a white m

, for example, an alpha cellulose paper _e exploit m paper around the unusually bright color of the melamine-formaldehyde reaction product. The paper can, for example, consist of 100 io alpha cellulose fiber or a mixture of alpha cellulose fiber and rayon fiber (in a mixing ratio between 40 and 60 fo) ,

The proportion of melamine-formaldehyde resin in the

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impregnated paper (eaten on dry:? Baals) canoe between 45 and 70 percent by weight * where the The rest of the impregnated paper consists of cellulose fibers.

In the impregnation process came the impregnated sr at a temperature between 115 ι can be dried for about a minute,

Paper at a temperature between 115 and 138 ° C

A laminate provided with such an impregnated cover layer is suitable for numerous applications, for example doors, table tops and other surfaces that should have a permanent, pleasing appearance _. in the production of tableware with a decorative top layer,

Manufacture of objects using the hot pressing process:

A typical laminate is i3t, a web made by hot pressing a number of resin impregnated paper layers. A paper layer impregnated according to the invention, which preferably consists of alpha cellulose paper, which is impregnated with a melamine-formaldehyde reaction product which is a water-soluble, acid-forming

or contains zinc sala, the top layer 109863/0286

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'- 13 form such a laminate sheet »

However, paper webs impregnated according to the invention can also form the cover layers of other laminates, in which the base body of the laminate, for example, fiber material contains., for example wood fibers «

If a web impregnated according to the invention is used as a cover layer (or cover layers) of a laminate. in this way, the surface has excellent fleece resistance and gloss durability % 'c ...

Example 2:

By reacting formaldehyde and melamine in three various molecular ratios were made according to the following Method three solution egg produced?

Melamine (1,261.3 parts) comes in a 37 piece. watery. Dissolved formaldehyde solution, which had been diluted with the amount of water shown in Table 1. Before the melamine was added, enough sodium hydroxide was added to the formaldehyde solution so that the pH of the clear loessimg between the melamine and the temperature rose to 93 ° C 7 * 9 wcvi 6.5 lay, then followed a Bäiekfii2.0 d <sr iosüng _t

until the addition of a drop of Jjö »uig ^ & ® 100 0a VJas-

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which led to turbidity at 38 ° C. The solution was then cooled to room temperature. The total amount of melamine and formaldehyde used in each of the three solutions thus prepared corresponded to the total amount of melamine and formaldehyde used for the reaction. Table 1 below shows the Place of weight of the 37 ^c p ± go.n aqueous forria! Dehyälösimg: "and the parts by weight of water for the preparation of the '.75- solution in the three cases mentioned, furthermore the Ί-lol number used for jecios moles of melamine porioaldehyri.

Table 1;

Lot of 37 $
Forraaldehyde solution V / s volume Molar ratio ari
shear. Formaldehyde
unü Kelamin 1055 987 1.30 1219 945 1.50 1380 903 ■ 1,, 70 .. ^!

To produce a erfindungsgemäßeri Lösimg a generated in the manner explained solution oiaea Melaminforrflal'Ishyd-Jleaktionsproduktes zugssetzt a lctenter Ann curing catalyst, L'ith the so · her / msteilten Lo sungwurde a web of Alphs ^ ellulosepapier s "import prägniept that the paper According to the Trookn <m a proportion of 67 to 69 ^l ß> Halaminformaldehydliarss 109883 / Oati

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The excess solvent "remaining on the surface of the impregnated paper was removed with the aid of scrapers and Print rollers removed. The impregnated paper was ^ during dried for one minute at 132 ° C »After drying Samples of the impregnated paper were subjected to a standard test using eight or nine paper webs pressed together at 150 ° C for two minutes lind the material surrounding the laminate that has flowed out removed and weighed. The weight of this material was between S and 12> 5 of the total weighta of the laminate including the material that has flowed outwards s »-

The dried impregnated web was then produced as a cover layer as a laminate in a pressing process Plate was initially used as a base body the plate is a conventional pressed part made of Kelaminformaldehyde Filled alpha cellulose produced * At its temperature of 157 ° C, a pressure of about 210 kg / cm and one The pressing time was then 45 seconds First a basic film was produced. The mold was then opened and the impregnated paper web on the top of this basic molding laid! laugh at that Close the mold then the mold during the exposed to the same pressure and the same temperature before the finished part was removed from the? orm *,.

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In comparison, the same process was used to manufacture a pressed laminate board with a laminate top layer made of alpha cellulose paper with 67 percent by weight of a thermosetting reaction product of formaldehyde and ilelamin in a Γίοΐ eyepiece ratio between 2: 1 and 2.5: 1 existed, for this one For comparison test, standard quality impregnating agent was used, as is the case for top layers of clay pressed dishes are used *

Each pressed board thus produced was sawn in half. One PJ. Mat half was immersed in a test bath which was prepared by adding 25 _f 4 g of powder coffee per liter of water. The test bath with these samples was then kept at a temperature of 82 ° C. for 48 hours. The test plates were then removed from the bath, rinsed with water and dried. Then it was the degree of pollution. (J ¹ IeCkC adhesion) of the top layer was determined in such a way that the reflection of blue light (475 Xt) of the plate half treated in the manner described was compared with the reflection of the untreated pure plate half using a Bauach-ob Lomb spectrophotometer.

The following table 2 gives the results of a 109883/0286

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Number of these attempts again. The table shows how many moles of formaldehyde per mole of melamine were used for the preparation of the impregnation solution, also the type of catalyst _{ the amount of the catalyst (expressed in percent by weight of the solution), the duration of the curing of the laminate molding at 157 ° G Introduction of the top layer as well as the Pleclren insensitivity (expressed as a percentage of the yeast reflection of blue light on the top layer of the 'seat piece, where the yeast action on the top layer of the untested test pieces is assumed to be $ 100) »

Table 2

1.30

1.50

1 * 30 a

1.30 η

1.50

catalyst

Aluminlumni stepped

Aluminum sulfate

Zinc acetate

Zinc chloride

Hardening - Pleekenuii-; duration sensitive- ■ M} 2 \ 91. : 1 '-. [ IB ■ 2 ; 92 -; 1
2 ■ ■ ^{; v} -67. ; 1 m 2: 1 . J 7 7 : 2 Bl 1 80 2 90

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16962Λ2

Moles
CH ₂ O catalyst Auahärt-
duration
(Minutes) Stain clamp
sensitive
Jceit ( per zen-'c) 1.30
It Zinc3ulphate (0, β $)
η ti 1
2 83
88 1.30.
ti Zinc nitrate (£ 0.6)
It Π 1
2 88
92 1.50
ti
η
ti Aluminum chlorine id (0 _: 5 $)
it n.
(ρ, m
It Il 1
2
1
2 82
90
91
91 1.50
η Altnainiumnxtr at (0.3 ? ° )
»Η 1 .
2 84
85 1.50
η Aluminum sulphate (0 * 6 ^)
ti n 1
2 71
73 1, f O
ti Zibacetate (1,2 ^)
n dd 1
2 55
76 η -
« I. Cial chloride (0.3 ^)
H Il
^tt (0.6 ^)
41 Il 1
2
1 '
2 84
90
93 1.50 ". I
it: Xiaaka nitrate. (0.6 ^) 1
2:: 37 I.
90 1.50!
ti: Zinc sulfate ($ 0.6)
η ti 1
2; ■ 70 ₄ ^;
78 1.70 I.
nt \ Alximialumciilorid ΐθ, 3 #)
λ ■ · η 1 ^; ? 5
B2 I. U 70!
H ; A1 | ΐιητ Pi μηιτι-ί hr svt (D, ^)
«Ill 1 ^;
2 -; ? 4 " ^l
m I 1.70 ^l Aluminum sulfate ($ 0-6)
t »» I. 1
2 & 2 \
71 ί 1.70;
ti 2iiikaz «-feat ($ 1.2)
n ·. « 1
2 56.
70

Moles
GH ₂ O catalyst Curing
duration
(Minutes) Leakage
sensitive ~
speed (percent) 1.70
Il
1"
ft Zinc chloride ($ 0.3)
ti tt
«(£ 0.6)
ir w 1
2
1
2 88
92
88
93 1.70
ί! Z inkni occurred (0 _v $ 6)
If Il 1
2 82
84 1.70
Il Zinc sulfate (0 655)
ti II 1
2 58
68 2.0
until
2.5 (Comparison test) 2 52

The search results shown in Table 2 Seigen «that the comparison parts show a strong sensitivity to stains It can be stated that a visual inspection of these parts of the equations showed that the lamina tdeckechiejit these Vercuchsstücke more dirty was than the uncovered underside of the part.

From the table above it can also be seen that: if a relatively low molecular ratio between formaldehyde and melamine, such as 1.3: 1, is used, a particularly high level of Pleke resistance is obtained; however, the product then cures rather slowly In practice, a storage space of the order of magnitude of ei, ii63 * Ilinute is satisfied- 109883/0288

BATH ORIGINAL

while a curing time of about two minutes should represent the limit of what is permissible.

A visual inspection of the with an inventive Parts provided with a laminate top layer showed that this top layer - in contrast to the underside of the parts - hardly Had spots and was not impaired in its gloss.

The pressed parts produced in the manner explained were also (instead of the previously explained immersion in a coffee solution) repeatedly rinsed in conventional rinsing water, various chlorinating pickling detergents were used, as they are commonly used for dishwashing. In this case, too, the cover layers of the plates produced according to the invention lasted much longer
their gloss than the laminate cover layers of the comparison plates produced in the customary manner. The rapid loss of gloss that occurs with the known top layers
is an indication that the Melaminforraeldehya-Harzachicht loses itself there relatively quickly, so that the cellulose fibers are exposed. However, once this state is reached, the laminate top layer is one
exposed to extremely strong and rapid pollution.

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Claims (1)

- 21 ■ ~
Pat entg as check ■■ _e ) Paper web for use as a laminate fabric in the manufacture of objects with high stain resistance and good gloss retention in a hot-pressing process, containing callulosic fibers which are thermosetting reaction products of formaldehyde and melamine in a molecular ratio between 1: 1 and 1.9: 1 are impregnated, characterized in that the cellulose fibers are at the same time impregnated with a water-soluble, acid-forming aluminum or zinc ate. 2o) paper web according to claim 1, characterized in that da.3 the molecular ratio between formaldehyde and melamine is between 1.2: 1 and UM, Jt) paper web of Claim 1, ·, characterized in that the cellulose fibers are impregnated da3 with a water soluble salt of a strong inorganic acid " 109883/02 «6 BATH l