CA1091836A - Aqueous solutions of etherified melamine-formaldehyde resins having long shelf life and low content of free formaldehyde - Google Patents
Aqueous solutions of etherified melamine-formaldehyde resins having long shelf life and low content of free formaldehydeInfo
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- CA1091836A CA1091836A CA251,045A CA251045A CA1091836A CA 1091836 A CA1091836 A CA 1091836A CA 251045 A CA251045 A CA 251045A CA 1091836 A CA1091836 A CA 1091836A
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- melamine
- solution
- formaldehyde
- temperature
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
- C03C25/00—Surface treatment of fibres or filaments made from glass, minerals or slags
- C03C25/10—Coating
- C03C25/24—Coatings containing organic materials
- C03C25/26—Macromolecular compounds or prepolymers
- C03C25/32—Macromolecular compounds or prepolymers obtained otherwise than by reactions involving only carbon-to-carbon unsaturated bonds
- C03C25/34—Condensation polymers of aldehydes, e.g. with phenols, ureas, melamines, amides or amines
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G12/00—Condensation polymers of aldehydes or ketones with only compounds containing hydrogen attached to nitrogen
- C08G12/02—Condensation polymers of aldehydes or ketones with only compounds containing hydrogen attached to nitrogen of aldehydes
- C08G12/40—Chemically modified polycondensates
- C08G12/42—Chemically modified polycondensates by etherifying
- C08G12/424—Chemically modified polycondensates by etherifying of polycondensates based on heterocyclic compounds
- C08G12/425—Chemically modified polycondensates by etherifying of polycondensates based on heterocyclic compounds based on triazines
- C08G12/427—Melamine
-
- D—TEXTILES; PAPER
- D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
- D06M—TREATMENT, NOT PROVIDED FOR ELSEWHERE IN CLASS D06, OF FIBRES, THREADS, YARNS, FABRICS, FEATHERS OR FIBROUS GOODS MADE FROM SUCH MATERIALS
- D06M15/00—Treating fibres, threads, yarns, fabrics, or fibrous goods made from such materials, with macromolecular compounds; Such treatment combined with mechanical treatment
- D06M15/19—Treating fibres, threads, yarns, fabrics, or fibrous goods made from such materials, with macromolecular compounds; Such treatment combined with mechanical treatment with synthetic macromolecular compounds
- D06M15/37—Macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
- D06M15/39—Aldehyde resins; Ketone resins; Polyacetals
- D06M15/423—Amino-aldehyde resins
- D06M15/427—Amino-aldehyde resins modified by alkoxylated compounds or alkylene oxides
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- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Organic Chemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Life Sciences & Earth Sciences (AREA)
- Health & Medical Sciences (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Textile Engineering (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Geochemistry & Mineralogy (AREA)
- Materials Engineering (AREA)
- Phenolic Resins Or Amino Resins (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
An etherified melamine-formaldehyde resin is disclosed that has prolonged shelf life, comparatively low free formaldehyde content, and is especially adapted as a binder for glass fiber mats. The melamine-formaldehyde resin is prepared in several distinct stages including condensation in a basic aqueous solution, etherification by cooling and acidification, neutralization with tri-ethanolamine, and final stabilization. The free formal-dehyde content of the resin so produced can be adjusted by reacting it with urea.
An etherified melamine-formaldehyde resin is disclosed that has prolonged shelf life, comparatively low free formaldehyde content, and is especially adapted as a binder for glass fiber mats. The melamine-formaldehyde resin is prepared in several distinct stages including condensation in a basic aqueous solution, etherification by cooling and acidification, neutralization with tri-ethanolamine, and final stabilization. The free formal-dehyde content of the resin so produced can be adjusted by reacting it with urea.
Description
10918~
FIELD OF TIIE INVF,NTION
The present invention rela~es to aqueous solu-tions of melamine-formaldehyde resins and methods for their ;~
preparation, and, more particularly, to etherified melamine-formaldehyde resins having long shelf lives and comparatively low contents of free formaldehyde. The melamine-formaldehyde resins are of particular utility as binders for glass fiber mats in the manufacture of various items.
OBJECTS OF THE INVENTION
.
It is an object of this invention to provide etherified melamine-formaldehyde resins and methods for their preparation.
Another object of this invention i5 to provide etherified melamine-formaldehyde resins that have prolonged -,"i shelf lives.
Another object is to provide in accordance with one aspect of this invention etherified melamine-formaldehyde resins that have low residual free formaldehyde.
Another object of this invention is to provide etherified melamine-formaldehyde resins that nave high water compatibility.
Another object of this invention is to provide a method for the preparation of etherified melamine-formaldehyde resins that can reproducibly be controlled.
Another object of this invention is to provide etherified melamine-formaldehyde resins that are especially suitable for use as binders for glass fiber mats.
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f~ ~
SU~ RY OF THE~ VEMTION
Briefly, these and other objects are achieved by conducting a reaction in a plurality of distinct . ~tages, including: ' ' .
~1) condensing a basic aqueous solution l ' of melamine and formaldehyde at elevated tempera-;' tures, to a controlled degree, in the presence of a polyol and triethanolamine;
~2) etherifying the aqueous condensate 0 by cooling and acidification;
:~¦ ' (3~ terminating the etherification by ¦ neutralizing ths cooled acidic solution with a base;j ¢omprised, at least in part, of triethanolamine;
. (4) stabilizing the neutralized solution by heating it to an elevated temperature for a con-'3; trolled period of time; and , ~ . ~ . .
5) adjusting the free formalaehyde con-~ tent of the stabilized solution by the addition .'i' r of urea.
The resins obtained by the practice of this ' invention are characterized by a particularly high ..
. ' formaldehyde-melamine molecular ratio (designated here-Inafter as "F/M ratio"), by good water compatibility, by a shelf life at ambient temperatures at least equal to ~1; two months, and by a content of free formaldehyde less 3 than 6% by weight. ~
`'~ . The term "water compatibility" is here defined ~¦ as the lar~est amount of water ~by vo'lume) that can be i added to 100 volumes of an agitated a~ucous resin solution '`'1 .
'`:1 'I .
., -- 2 -- .
at 25C before the first appearance of turbidity.
The term "shelf life at ambient temperatures"
denotes the ability of an aqueous resin solution, when stored at ambient temperatures between 15C and 25C, to maintain both a viscosity, measured at 2SC, of less than 800 centipoise ,and a water compatibility greater than or equal to 1,200. The aqueous resin solutions w,hich are the obiect of this invention have useful shelf lives of at least two months.
These resins, together with a suitable sizing, are particularly suitable for use as a binder for glass fiber mats, The aqueous solutions of this invention provide excellent properties for glass iber mats, such as improved stress resistance and flexibility.
DESCRIPTION OF THE PPIOR ART
The preparation of etherified melamine-formal-dehyde resins is known in the prior art as disclosed, for example, in German patent application No. 2,005,166, published for public inspection on February 5, 1970.
This application discloses a process for the alkaline condensation of melamine with formaldehyde in the presence of a polyol, by which process practically anhydrous ether-ified tetramethylolmelamines or tetramethylolmelamines in alcohol solution are obtained.
The process of this German application can be distinguished from the instant invention in that the, ~nstand invention provides substantially higher P/M
ratios, the ratio of moles diol to moles melamine i~
higher, the ratio of moles of triethanolamine to melamine ~ ' ' , ' 1091~336 i5 higher and the alkaline condensation is conducted at lower temperatures. Further, the instant invention relies substantially on polyols or etherification whexeas the German disclosure primarily utilizes mono-hydric alcohols for this purpose.
Another prior art method for the preparation of resins of the type with which this invention i5 con-cerned is described in U. S. Patent 2,577,767 in which triethanolamine is also included in the reactive melamine-formaldehyde-polyol mixture. In this process, an initial reaction is conducted at a relatively high temperature ~80C), the reacting mixture is acidified to a pH of between 0.5 and 1.5 at eleva~ed temperatures ~72-82C), and a ~inal step includes increasing the pH of the resin , .
to about 6.3 with sodium hydroxide, also at elevated t~n-peratures (70C). The process disclosed in this patent i~ conducted under rather ex~reme conditions of pH and temperature, making it difficult, at very best, to exer-! cise reproducible control over residual formaldehyde,1 20 viscosities and shelf life of the resins as can be done ¦ in the practice of the instant invention.
'¦ DETAILED DESCRIPTION OF TEIE INVENTION
; First Stage - Conden~ation . .
The melamine employed in this invention can be of technical quality, but must have a purity of greater than 99% by weight, with the maiority of particles le5s ¦ than 160 microns in diameter to permit facile dissolution - ~n the reaction environment.
While either formaldehyde or its polymers (such . as paraformaldehyde) can be used in the practice of this ~ ' ' ' . .
4 _ 109i83~ .
-.invention, 36% by weight aqueous solu~ion of formalde-hyde preferably is employed due to its comm~rcial avail-ability and its comparatively low cost. These solutions ; . ~hould not contain more than 10% ~maximum) methanol ~y weight. Preferably, this content will be less than 1%
in order to avoid the presence of methoxy groups in the etherified resin. In practice, etherification is pre-ferably achieved solely by a polyol or triethanolamine rather than by monofunctional alcohol.
The F/M ratio will range between 5 and ll, but preferably between 6.5 and 10. Values lower than 5 cause `I a lo~s in glass fiber mat properties ~particularly stress ~ésistance) and further result in low water compatibility :~i value~. Values higher than 10 yield final aqueous solu-! tions with low dry extracts which have little industrial ;. I
. . use. The successive values 5, 6.5, 10 and 11 of the F/M
,;~ ratio correspond appreciably to the dry extracts which , are 52, 50, 44 and 41% respectively, if one uses as a I source of formaldehyde an aqueous solution of 36% by j 20 weight.
-¦ . The alkaline condensation reaction is éffected ; at a p~ ranging between 8.5 and 9.5 and preferably between . ' 8.8 and 9.2. This pH is obtained by addition of triethan-olamine to the reacting environment.
~ he quantity of triethanolamine will range between 0.2 and 0.6 and preferably between 0.3 and 0.4 ~ molecule per molecule o~ melamine. This ratio will be .
designated hereinbelow by the ratio TEA/Mo These quanti-t~es are largely in excess in relation to that re~uircd ' . .' ,~
0 5_ 10~1836 for adjustment of the reacting p~i at the values indicated.
~heir purpose is to provide resins ~as already mentioned) with high water compatibility.
Also included with aqueous condensation reac-tants is a polyol, such as ethylene glycol, in an amount corresponding to a polyol/me~amine molar ratio of from about 3 to about 5, and preferably from about 3.5 to about .. . . .
4Ø
he reaction is preferably conducted as follows:
- First, the required quantities of formaldehyde, polyol and triethanolamine are mixed and then, with vigor- -OU5 agitation, the mixture is brought to the desired reac-tion temperature, ranging between 60C and 70C, and pre-I ~erably b~tween 63c ana 68c.
! Second, the melamine is gradually added over a ~ period of ten to fiftéen minutes while maintaining the j ~ desired reaction temperature and solution agitation for ¦ a further period of thirty to ninety minutes. Tempera-tures of at least 60C are necessary to dissolve the mela--¦ 20 mine at a practical rate.
At the appropriate time (as discussed below), the reaction is stopped by cooling the mixture to a tem-perature ranging between 20C and 40C, and preferably between 33C and 37C.
The reaction is stopped by rapid cooling at a precise moment which is determined by the cloud point of ~he-rcacting mix that is measured and monitored during ~heLreaction.
his cloud point is indicative of thc extent .
.
'',I
: j .
- 109i836 .
of the alkaline condensation. It is measured by suc-cessivc samplings of test pieces from the reacting ~nvironment at regular time intervals. These test pieces are cooled while agitating them and the temperature at which a cloud i5 produced is noted. This cloud point temperature, rather low at the beginning of the reaction, rises as the reaction proceeds.
The alkaline condensation reaction is stopped by rapid cooling when the cloud point appears between 40 and 65C, and preferably between 45 and 55C, which : i5 produced at the end of a time period usually in a range of from 30 to 90 minutes.
I the reaction is stopped at a cloud point le~s than 40C, the cooled reacting environment then presents a high ~iscosity which makes it difficult to maintain homogeneity by agitation. At the other extreme, , , one cannot surpass a cloud point temperature higher than ' that of the reaction without causing the reacting environ-- ment to opacify at the reacting temperature. For example, ~; 20 if the temperature of the reaction is 70C, it would be very difficult to measure a cloud point temperature higher than 65C because of the small temperature difference betweén the test and reaction temperatures.
1 Second Stage - Etherification i In this stage, the methylolmelamines obtained in phase 1 are etherified with one or several of the polyols that were previously introduced into the reacting en~ironment. These polyols can be selected from, for ; example, ethylene glycols, diethylene glycol, triethylene '''I ' . .
`I , ' '.
1 i '",1 - ~
iO9i836 , , .
glycol, glycerol, saccharose and d-glucose. The pr~-~erred diol, because of its price and availability is ethylenc glycol.
Control over viscosities can be exercised by using mixtures of polyols. For example, by using a mix-ture of ethylene glycol and saccharose, the viscosity of the final resin will increase with an increased use :- of saccharose.
The total quantity of the one or several polyols ~
10 used should range between 3.0 and 5.0, and preferably ~--between 3.5 and 4.0 moles per mole of melamine. This ratio will be designated hereinbelow by the ratio P/M.
An lnsufficient ~uantity of polyol will diminish the resin's water compatibility. On the other hand, exceeding this ratio i5 not use~ul because it does not further increase ,.;
water compatibility.
The acid used for lowering the pH of the con-densation phase to that o~ the etherification should pre-~? ferably be a concentrated acid to avoid lowering the final ary extract of the aqueous resin solution. Examples of suitable acids are sulfuric, hydrochloric, orthophosphoric, nitric, formic or monochloracetic.
Immediately after the alkaline condensation, ::~, the mixture is cooled, as described above, ~nd, while maintaining the obtained temperature constant, the envir-onment is acidified to a p~I selected with regard to th~
chosen temperature, the pll range being 1.5 to 3Ø It ~s under these conditions of temperature and p}I that the atherification reaction is effected.
.
'~' , ~ .
The conditions should range between 25°C
for a pH of 1.5 to 40°C for a pH of 3.0, or preferably 33°C for a pH of 1.8 to 37°C for a pH of 2.2.
If etherification is conducted at a pH and/or a temperature that is too high, the resin will have a viscosity which is too high. It will also reduce shelf life and hinder use of the resin soon after preparation.
On the other hand, if the pH and/or temperature of ether-ification is too low, the viscosity of the resin will be low, its water compatibility will be very good, ut the values of stress resistance for the glass fiber mats will be undersirably low.
After acidification, the temperature of the cloud point at which the reacting environment, previously opaque, becomes clear, is determined. The etherification reaction is then continued for a certain time at the same temperature before stopping it by neutralization.
The time periods before and after the moment when the reacting environment becomes clear will be called hereinafter "opaque phase" and "clear phase" of etherification.
The following conditions should be respected for the etherification pahse: The acid should be added very regularly and for a period between 25 and 35 minutes, preferably between 28 and 32 minutes.
It has been found that the total duration of etherification is substantially constant, and that by final viscosity of the aqueous resin solution is appre-i09i83~
ciably increased. On the other hand, the acid should be added slowly enough to permit adequate mixing and to maintain a constant temperature despite any heat released by the acid addition. -~
The total duration of etherification, counted f~om the outset of the acid addition, should range be-tween 50 and 180 minutes for a cloud point ranging be-tween 40 and 65C, respectively, and preferably between 105 and 135 minutes for a cloud point ranging bet~leen 45 10 and 55C respectively. These duration Iimits are under-stood to be true in the context of the previously defined values o f pH and temperature.
For the pH and temperature values indicated hsr~inabove for the cloud point, it has been established that the minimal duration of the opaque phase is 50 min-utes, measured from the beginning of the acid flow.
If, on the other hand, at pH and temperature values indicated hereinabove for the cloud point, a total duration of 180 minutes is surpassed, it has been estab-20 lished that the viscosity of the resins becomes too greatand that their water compatibility falls below 1,200 immediateiy after manufacture. Further, it can be shown that when these resins are maintained at storage tempera-tures, there is a rapid increase in their viscosity and an equally rapid lessening of their water compatibility.
After their manufacture, the resins of the pre-sent invention have low viscositics ranging betwecn about 30 and about 200 centipoise.
It should be remembered that to obtain the , iV~1836 minimal shelf life of two months and a water compatibi-lity of at least 1,200, the viscosity of the resins ~hould not be higher than 800 centipoise. As is known, dur~ng storage the resins tend to increase their viscos-ity and to diminish their water compatibility.
Third Stage - Neutralization of Etherified Resin Upon completion of the etherification and reaching an appropriate cloud point, as mentio~ed above, the aqueous resins are neutralized to a pH of about 7.0 to 7.5. The base employed for neutralization should be triethanolamine. Minimally, triethanolamine should be present at a ratio of 1/3 mole per mole of melamine; the rest of the neutralizing agent can be a base such as a solution o 5G% by weight sodium hydroxide.
It has been established that the total neutral-ization by soda yields resins not easily miscible in water and precipitation occurs due to the neutralization.
The purpose of neutralizing with triethanolamine is to Lmprove the water compatibility of the resin.
Fourth Stage - Stabilization - This stage of preparation of the resins of this invention is one in which the reacted mix is held at ele-vated temperatures of 50C to 90C, and preferably between 70C and 85C, for a period of time of about two to five hours. This holding period ~herein referred to as "sta-bilization") is important because it improves two proper-t~es of glass fiber mats held together with a binder pre-pared from the-aquc~us resin solutions. It has been found that increasing the duration of this stabilization stage 109i~36 . :~:
', '' ~-increases the flexibility index and stress resistance of the glass fiber mats.
The 1exibility index and stress resistance were determined in accordance with the following:
Sixty rectangular test pieces measuring 25 x S cm were cut from a glass fiber mat. On thirty of these test pieces, stress resistance was measured and the aver-age of these measurements taken.
The other thirty test pieces were each sub- -jected one time to folding under the following condi-tions. A metal plate was used which was 35 cm long and S cm wide, of 2 mm thickness, and supplied with two hin~es which permit folding it into two half-plates, each 12.5 cm long. Each flat mat test piece was placed ~ -on the unfolded plate and two other plates measuring 12.5 x S cm were applied over the mat~ The test piece was maintained tightly closed and flat between the plate supplied with hinges and the two half-plates completely folded 180 around the hinge. The distance between the two halves of the test pieces after folding was 10 mm, the test piece always being maintained between the plates, as described. The stress resistance of the thirty test pieces was measured and the average of these measurements taken. The loss of traction resistance after folding was then calculated in percentage.
The flexibility index is a numbcr on a scale of 0 to 10 which was determined in accordance with the following table:
, 1091~336 Loss of Stress Resistance Flexibility after Folding in % Index -0 to 4 10 4 to 10 10 to 20 8 20 to 30 7 3~ to 40 6 40 to 50 ~ 5 `
50 to 60 4 60 to 70 3 70 to 80 2 80 to gO
90 to 100 0 A ~mall lessening in percentage o~ free for-maldehyde of the aqueous resin solution and a gradual increase in its viscosity is observed during the stabil-ization stage. Since this may be detrimen~al to the shelf life of the resin solution, the stabilization is l~mited to the above-mentioned temperature ranges of 50C
to 90C, and preferably of 70C to 85C, for a period of time not to exceed two to five hours.
Under these conditions, the aqueous resin solution remains water compatible at a ratio of at least 12 times its volume.
If the duration of the stabilization period surpasses five hours, for the indicated temperature values, the resin acquires an undesirably high viscosity. If the 8tabilization is interrupted before two hours, the desired improvement in flexibility of glass fiber mats is not obtained.
.
Fifth Stage - Reduction of Free Formaldéhyde Th~ percentage of free formaldehyde of the aqueous rcsin solutions after the stabilization stage is even higher than the initial F/M ratio and is on the order of 6 to 12% or more. Such amounts of free formaldehyde are undesirable because, among other reasons, the vapors emitted during final curing irritate the eyes and respir-atory systems of the operators.
Thus, the principal objective of the fifth ,-~tage is to reduce the content of free formaldehyde to 6% or less. The irritating vapors emitted at these con-centrations are tolerable to the worker~.
Further, when the ~ormaldehyde content of the resin is reduced to 6~ or less, the stress re~istance o the resin-bonded glass fiber mats increases and the rate at which the viscosity of the stored aqueous resin solu-tions increases is minimized, thereby contributing to a prolonged shelf life.
The free formaldehyde content is reduced in the fifth phase by adding urea in a ratio of 0.6 to 1.6, and preferably 0.8 to 1.2 moles of urea per molc of melamine while the resin is heated to temperaturés as existed in the stabilization stage. The free formaldehyde content of the stabilized resin is a function of the initial F/M
ratio and therefore the molecular ratio of urea to mela-mine is referred to here as the U/M ratio.
.
109183~i EX~MPLE 1 Stage I
562 g of an aqueous solution o~ 36% formaldehyde and 0.5% methanol, 248 g of ethylene glycol and 49.5 g of triethanolamine were introduced into a one-liter reactor ~upplied with a reflux condenser, an agitator and a thermometer. The solution was heated to 65C and 126 g of melamine were added in twelve minutes during agitation.
The condensation reaction was continued at 65C until a cloud point of 50C was obtained, at which time the tem-. perature was rapidly lowered to 35C.
Stage II
, Etherification was commenced by adding 56 g of concentrated sulfuric acid over a thirty-minute period until a pH o 2 was reached. Etherification continued at 35C for one hour and thirty minutes.
Stage III
At the end of etherification, the p~ of the environment was adjusted to 7.2 by adding 49.5 g of tri-ethanolamine and 50 g of a 50% solution of sodium hydroxide.
- Stage IV
The temperature was then brought to 70C and the resin allowed to stabilize for five hours.
Stage V
At the end of five hours, 48 g of urea were introduced and the resin cooled to a temperature of about 60C.
- The rcsin obtained presented the following~
charactcristics:
. .
.. . . . . ..
1(~9~836 - :
- F/M ratio - 6.75 - P/M ratio ~ 4 - TEA/M - 0.33 - Number o molecules of triethanolamine, added after etherification, per molecule of melamine:
0.33 - U/M ratio = 0.8 - Dry extract: 50.1%
- Viscosity: 94 centipoise - -~
- Free formaldehyde: 1.9 - Water compatibility: infinite ~2,000) - pH: 7. 2 - After two months' storage: Infinite water com-patibility (~2,000) and a v~scosity of 160 cen-tipoise PreParation of S~zing An aqueous dispersion of starch paste was pre- -pared from potatoes, as modified by ethylene oxide treatment, having a concent~ation of 8% calculated in the form of anhydrous starch. Steam was bubbled in this dispersion until its temperature reached 98C and was -continued for twenty minutes. After cooling to 25-30C, the paste was ready to be used.
An aqueous solution of the preceding melaminé-formaldehyde resin corresponding to a dry weight of 1.2 kg was mixed with 110 Xg of the paste MLxed with the preceding mixture was an emul-sion of a homopolymer of polyvinyl acetate, which poly-vinyl acetate was plasticized by dibutyl phthalate to the extent of 50~ of plasticizer p~r weight of resin.
1.378 kg of a 58% emulsion, based on the dry weight of the plasticizcd homopolymcr~ was mixed with 1.378 kg (or an equal weight) of water and the resulting mixture added to the mixture of starch and melamine-formalde-hyde resin formed in the preceding step.
The diluted emuision was added to the preceding mix. The total was homogenized by agitation or ten minutes and constituted the concentrated sizing.
; When used, this concentrated sizing was diluted by a quantity of water such that the sizing finally used had a dry extract of 2.2%.
Preparation of a Glass Fiber Mat A mat of unbonded discontinuous glass fibers (hereinafter called "uncured mat") was used. This mat was obtained by distributina in regular fashion on a conveyor belt of metallic cloth discontinuous glass fibers obtained by steam attenuation of molten glass streams which flow from holes placed at the lower sec-tion of a platinum bushingO These glass fibers have an ~verage diameter of about 16 microns. The uncured ma~
used had a weight of 80~5g/m2.
The uncured mat, in the form of a continuous ribbon placed between two conveyor belts of metallic cloth, was immersed in the preceding prepared sizing.
The excess sizing retained by the uncured mat was extracted, always in a continuous fashion, by means of a bin with a depression placed below the lower belt.
The deprcssion was regulated in the bin so that the mat retained, after drying, 20~ by weight of dry binder in proportion to the total weigkt of glass and dry binder.
The uncured mat, sized and dried, was then con-109i83~
tinuously passed for two minutes in an air circulation ov~n heated to 145C.
The finished mat was found to have a stress resistance of 5.5 kg/cm and a flexibility index of 7.
A melamine-formaldehyde resin was prepared according to the operative mode of Example 1, using the following quantities of materials:
- formaldehyde at 36% 666 g - ethylene glycol 248 g :
- triethanolamine 49.5 g - melamine 126 g ~, - concentrated sulfuric acid 56 g ;
- aqueous solution of sod~um 50 g hydroxide at 50%
- urea 48 g ;
- triethanolamine 49.5 g The resin obtained had the following charac-teristics:
- 20 - F/M ratio: 8.0 - P/M ratio: 4.0 - TEA/M ratio: 0.33 - Number of molecules of triethanolamine, added after etherification, per molecule of melamine:
0.33 - U/M: 0.8 - Dry.extract: 47.8%
- - Viscosity: 70 centipoise . - Free forma~dchyde: 4.0~
, - Water compatibility: infinite ~2,000) - pH: 7.2 , lOgl83~ " `, - After two months' storage: Infinite water com-patibility (~2,000) and a ~iscosity of 130 centipoise.
By u~ing the preceding resin, a paste was pre-pared that was applied on the uncured mat which was then dried in an oven according to the method described in Example 1.
The stress resistance of the final mat was 5.6 kg/cm and the flexibility index was 7.
EXAMPLE 3 f A melamine-formaldehyde resin was prepared according to the method of Example 1, using the quan-t~ties of materials set forth below:
- ~ormaldehyde at 36% 750 g - ethylene glycol 248 g - triethanolamine 49.5 g - melamine 126 g - concentrated s~lfuric acid 5~ g .
- triethanolamine 49.5 g - aqueous solution of sodium 50 g hydroxide at 50%
- .urea 48 g The characteristics of this resin were as fol-lows: .
- F/M ratio: 9.0 - P/M ratio: 4.0 - TEA/M ratio: 0.33 - Number of triethanolamine moleculesJ added after etherification, per molecule of melamine: 0.33 3n U/M ratio: 0.8 - Dry extract: 45.6%
109183~
- Viscosity: 52 centipoise - Free formaldehyde: 5.4%
- Water compatibility: infinite (~2,000) _ p~ 7.2 - After two months' storage: In~inite water com-patibility ~2,000) and a viscosity of 100 cen-tipoise.
By using the preceding resin, a sizing was prepared th~t was applied to the uncured mat which was then dried in an oven according to the method described in Example 1.
Ths finished mat had a stress resistance of 5.9 ~g/cm and a flexibility index of 8.
~XAMPLE 4 . A formaldehyae-melamine resin was prepared -:
according to the method of Example 1, using the follow-ing quantities of materials:
- formaldehyde at 36~ 6b6.5 g - ethylene glycol 198.5 g - triethanolamine 39.5 g - melamine 101.0 g - concentrated sulfuric acid45.0 g - triethanolamine 39.5 g - aqueous solution of sodium40.0 g hydroxide at 50% .
urea 38.5 g The characteristics of this resin were as fol-lows: ~ -- F/M ratio: 10.0 - P/M ratio: 4.0 - TEA/M ratio: 0.33 .
, - Number of triethanolamine molecules, added aftcr ethexification, per molecule of melamine: 0.33 - U/M ratio: 0.8 - Dry extract: 43.2%
- Viscosity: 44 centipoise - Free formaldehyde: 5.7 - Water compatibility: infinite (~2,000) - pH: 7.2 , - After two months' storage: Infinite water com-- - patibility (~2,000) and a viscosity of 92 cen-tipoise.
A sizing was prepared by using the preceding resin and then a mat manufactured according to the method of Example 1. This mat had a stress resistance o~ 6.2 kg/cm and a ~lexibility index o~ 7.
. * * *
If the stress resistances of the mats obtained in Examples 1, 2, 3 and 4 are compared, the relationshi~ -between a rise in stress resistance with increasing F/M
, . .
ratios can be seen.
Stress Resis-Example F/M Ratio tance (kg/cm) 1 6~75 5.5 ,
FIELD OF TIIE INVF,NTION
The present invention rela~es to aqueous solu-tions of melamine-formaldehyde resins and methods for their ;~
preparation, and, more particularly, to etherified melamine-formaldehyde resins having long shelf lives and comparatively low contents of free formaldehyde. The melamine-formaldehyde resins are of particular utility as binders for glass fiber mats in the manufacture of various items.
OBJECTS OF THE INVENTION
.
It is an object of this invention to provide etherified melamine-formaldehyde resins and methods for their preparation.
Another object of this invention i5 to provide etherified melamine-formaldehyde resins that have prolonged -,"i shelf lives.
Another object is to provide in accordance with one aspect of this invention etherified melamine-formaldehyde resins that have low residual free formaldehyde.
Another object of this invention is to provide etherified melamine-formaldehyde resins that nave high water compatibility.
Another object of this invention is to provide a method for the preparation of etherified melamine-formaldehyde resins that can reproducibly be controlled.
Another object of this invention is to provide etherified melamine-formaldehyde resins that are especially suitable for use as binders for glass fiber mats.
.
~D
f~ ~
SU~ RY OF THE~ VEMTION
Briefly, these and other objects are achieved by conducting a reaction in a plurality of distinct . ~tages, including: ' ' .
~1) condensing a basic aqueous solution l ' of melamine and formaldehyde at elevated tempera-;' tures, to a controlled degree, in the presence of a polyol and triethanolamine;
~2) etherifying the aqueous condensate 0 by cooling and acidification;
:~¦ ' (3~ terminating the etherification by ¦ neutralizing ths cooled acidic solution with a base;j ¢omprised, at least in part, of triethanolamine;
. (4) stabilizing the neutralized solution by heating it to an elevated temperature for a con-'3; trolled period of time; and , ~ . ~ . .
5) adjusting the free formalaehyde con-~ tent of the stabilized solution by the addition .'i' r of urea.
The resins obtained by the practice of this ' invention are characterized by a particularly high ..
. ' formaldehyde-melamine molecular ratio (designated here-Inafter as "F/M ratio"), by good water compatibility, by a shelf life at ambient temperatures at least equal to ~1; two months, and by a content of free formaldehyde less 3 than 6% by weight. ~
`'~ . The term "water compatibility" is here defined ~¦ as the lar~est amount of water ~by vo'lume) that can be i added to 100 volumes of an agitated a~ucous resin solution '`'1 .
'`:1 'I .
., -- 2 -- .
at 25C before the first appearance of turbidity.
The term "shelf life at ambient temperatures"
denotes the ability of an aqueous resin solution, when stored at ambient temperatures between 15C and 25C, to maintain both a viscosity, measured at 2SC, of less than 800 centipoise ,and a water compatibility greater than or equal to 1,200. The aqueous resin solutions w,hich are the obiect of this invention have useful shelf lives of at least two months.
These resins, together with a suitable sizing, are particularly suitable for use as a binder for glass fiber mats, The aqueous solutions of this invention provide excellent properties for glass iber mats, such as improved stress resistance and flexibility.
DESCRIPTION OF THE PPIOR ART
The preparation of etherified melamine-formal-dehyde resins is known in the prior art as disclosed, for example, in German patent application No. 2,005,166, published for public inspection on February 5, 1970.
This application discloses a process for the alkaline condensation of melamine with formaldehyde in the presence of a polyol, by which process practically anhydrous ether-ified tetramethylolmelamines or tetramethylolmelamines in alcohol solution are obtained.
The process of this German application can be distinguished from the instant invention in that the, ~nstand invention provides substantially higher P/M
ratios, the ratio of moles diol to moles melamine i~
higher, the ratio of moles of triethanolamine to melamine ~ ' ' , ' 1091~336 i5 higher and the alkaline condensation is conducted at lower temperatures. Further, the instant invention relies substantially on polyols or etherification whexeas the German disclosure primarily utilizes mono-hydric alcohols for this purpose.
Another prior art method for the preparation of resins of the type with which this invention i5 con-cerned is described in U. S. Patent 2,577,767 in which triethanolamine is also included in the reactive melamine-formaldehyde-polyol mixture. In this process, an initial reaction is conducted at a relatively high temperature ~80C), the reacting mixture is acidified to a pH of between 0.5 and 1.5 at eleva~ed temperatures ~72-82C), and a ~inal step includes increasing the pH of the resin , .
to about 6.3 with sodium hydroxide, also at elevated t~n-peratures (70C). The process disclosed in this patent i~ conducted under rather ex~reme conditions of pH and temperature, making it difficult, at very best, to exer-! cise reproducible control over residual formaldehyde,1 20 viscosities and shelf life of the resins as can be done ¦ in the practice of the instant invention.
'¦ DETAILED DESCRIPTION OF TEIE INVENTION
; First Stage - Conden~ation . .
The melamine employed in this invention can be of technical quality, but must have a purity of greater than 99% by weight, with the maiority of particles le5s ¦ than 160 microns in diameter to permit facile dissolution - ~n the reaction environment.
While either formaldehyde or its polymers (such . as paraformaldehyde) can be used in the practice of this ~ ' ' ' . .
4 _ 109i83~ .
-.invention, 36% by weight aqueous solu~ion of formalde-hyde preferably is employed due to its comm~rcial avail-ability and its comparatively low cost. These solutions ; . ~hould not contain more than 10% ~maximum) methanol ~y weight. Preferably, this content will be less than 1%
in order to avoid the presence of methoxy groups in the etherified resin. In practice, etherification is pre-ferably achieved solely by a polyol or triethanolamine rather than by monofunctional alcohol.
The F/M ratio will range between 5 and ll, but preferably between 6.5 and 10. Values lower than 5 cause `I a lo~s in glass fiber mat properties ~particularly stress ~ésistance) and further result in low water compatibility :~i value~. Values higher than 10 yield final aqueous solu-! tions with low dry extracts which have little industrial ;. I
. . use. The successive values 5, 6.5, 10 and 11 of the F/M
,;~ ratio correspond appreciably to the dry extracts which , are 52, 50, 44 and 41% respectively, if one uses as a I source of formaldehyde an aqueous solution of 36% by j 20 weight.
-¦ . The alkaline condensation reaction is éffected ; at a p~ ranging between 8.5 and 9.5 and preferably between . ' 8.8 and 9.2. This pH is obtained by addition of triethan-olamine to the reacting environment.
~ he quantity of triethanolamine will range between 0.2 and 0.6 and preferably between 0.3 and 0.4 ~ molecule per molecule o~ melamine. This ratio will be .
designated hereinbelow by the ratio TEA/Mo These quanti-t~es are largely in excess in relation to that re~uircd ' . .' ,~
0 5_ 10~1836 for adjustment of the reacting p~i at the values indicated.
~heir purpose is to provide resins ~as already mentioned) with high water compatibility.
Also included with aqueous condensation reac-tants is a polyol, such as ethylene glycol, in an amount corresponding to a polyol/me~amine molar ratio of from about 3 to about 5, and preferably from about 3.5 to about .. . . .
4Ø
he reaction is preferably conducted as follows:
- First, the required quantities of formaldehyde, polyol and triethanolamine are mixed and then, with vigor- -OU5 agitation, the mixture is brought to the desired reac-tion temperature, ranging between 60C and 70C, and pre-I ~erably b~tween 63c ana 68c.
! Second, the melamine is gradually added over a ~ period of ten to fiftéen minutes while maintaining the j ~ desired reaction temperature and solution agitation for ¦ a further period of thirty to ninety minutes. Tempera-tures of at least 60C are necessary to dissolve the mela--¦ 20 mine at a practical rate.
At the appropriate time (as discussed below), the reaction is stopped by cooling the mixture to a tem-perature ranging between 20C and 40C, and preferably between 33C and 37C.
The reaction is stopped by rapid cooling at a precise moment which is determined by the cloud point of ~he-rcacting mix that is measured and monitored during ~heLreaction.
his cloud point is indicative of thc extent .
.
'',I
: j .
- 109i836 .
of the alkaline condensation. It is measured by suc-cessivc samplings of test pieces from the reacting ~nvironment at regular time intervals. These test pieces are cooled while agitating them and the temperature at which a cloud i5 produced is noted. This cloud point temperature, rather low at the beginning of the reaction, rises as the reaction proceeds.
The alkaline condensation reaction is stopped by rapid cooling when the cloud point appears between 40 and 65C, and preferably between 45 and 55C, which : i5 produced at the end of a time period usually in a range of from 30 to 90 minutes.
I the reaction is stopped at a cloud point le~s than 40C, the cooled reacting environment then presents a high ~iscosity which makes it difficult to maintain homogeneity by agitation. At the other extreme, , , one cannot surpass a cloud point temperature higher than ' that of the reaction without causing the reacting environ-- ment to opacify at the reacting temperature. For example, ~; 20 if the temperature of the reaction is 70C, it would be very difficult to measure a cloud point temperature higher than 65C because of the small temperature difference betweén the test and reaction temperatures.
1 Second Stage - Etherification i In this stage, the methylolmelamines obtained in phase 1 are etherified with one or several of the polyols that were previously introduced into the reacting en~ironment. These polyols can be selected from, for ; example, ethylene glycols, diethylene glycol, triethylene '''I ' . .
`I , ' '.
1 i '",1 - ~
iO9i836 , , .
glycol, glycerol, saccharose and d-glucose. The pr~-~erred diol, because of its price and availability is ethylenc glycol.
Control over viscosities can be exercised by using mixtures of polyols. For example, by using a mix-ture of ethylene glycol and saccharose, the viscosity of the final resin will increase with an increased use :- of saccharose.
The total quantity of the one or several polyols ~
10 used should range between 3.0 and 5.0, and preferably ~--between 3.5 and 4.0 moles per mole of melamine. This ratio will be designated hereinbelow by the ratio P/M.
An lnsufficient ~uantity of polyol will diminish the resin's water compatibility. On the other hand, exceeding this ratio i5 not use~ul because it does not further increase ,.;
water compatibility.
The acid used for lowering the pH of the con-densation phase to that o~ the etherification should pre-~? ferably be a concentrated acid to avoid lowering the final ary extract of the aqueous resin solution. Examples of suitable acids are sulfuric, hydrochloric, orthophosphoric, nitric, formic or monochloracetic.
Immediately after the alkaline condensation, ::~, the mixture is cooled, as described above, ~nd, while maintaining the obtained temperature constant, the envir-onment is acidified to a p~I selected with regard to th~
chosen temperature, the pll range being 1.5 to 3Ø It ~s under these conditions of temperature and p}I that the atherification reaction is effected.
.
'~' , ~ .
The conditions should range between 25°C
for a pH of 1.5 to 40°C for a pH of 3.0, or preferably 33°C for a pH of 1.8 to 37°C for a pH of 2.2.
If etherification is conducted at a pH and/or a temperature that is too high, the resin will have a viscosity which is too high. It will also reduce shelf life and hinder use of the resin soon after preparation.
On the other hand, if the pH and/or temperature of ether-ification is too low, the viscosity of the resin will be low, its water compatibility will be very good, ut the values of stress resistance for the glass fiber mats will be undersirably low.
After acidification, the temperature of the cloud point at which the reacting environment, previously opaque, becomes clear, is determined. The etherification reaction is then continued for a certain time at the same temperature before stopping it by neutralization.
The time periods before and after the moment when the reacting environment becomes clear will be called hereinafter "opaque phase" and "clear phase" of etherification.
The following conditions should be respected for the etherification pahse: The acid should be added very regularly and for a period between 25 and 35 minutes, preferably between 28 and 32 minutes.
It has been found that the total duration of etherification is substantially constant, and that by final viscosity of the aqueous resin solution is appre-i09i83~
ciably increased. On the other hand, the acid should be added slowly enough to permit adequate mixing and to maintain a constant temperature despite any heat released by the acid addition. -~
The total duration of etherification, counted f~om the outset of the acid addition, should range be-tween 50 and 180 minutes for a cloud point ranging be-tween 40 and 65C, respectively, and preferably between 105 and 135 minutes for a cloud point ranging bet~leen 45 10 and 55C respectively. These duration Iimits are under-stood to be true in the context of the previously defined values o f pH and temperature.
For the pH and temperature values indicated hsr~inabove for the cloud point, it has been established that the minimal duration of the opaque phase is 50 min-utes, measured from the beginning of the acid flow.
If, on the other hand, at pH and temperature values indicated hereinabove for the cloud point, a total duration of 180 minutes is surpassed, it has been estab-20 lished that the viscosity of the resins becomes too greatand that their water compatibility falls below 1,200 immediateiy after manufacture. Further, it can be shown that when these resins are maintained at storage tempera-tures, there is a rapid increase in their viscosity and an equally rapid lessening of their water compatibility.
After their manufacture, the resins of the pre-sent invention have low viscositics ranging betwecn about 30 and about 200 centipoise.
It should be remembered that to obtain the , iV~1836 minimal shelf life of two months and a water compatibi-lity of at least 1,200, the viscosity of the resins ~hould not be higher than 800 centipoise. As is known, dur~ng storage the resins tend to increase their viscos-ity and to diminish their water compatibility.
Third Stage - Neutralization of Etherified Resin Upon completion of the etherification and reaching an appropriate cloud point, as mentio~ed above, the aqueous resins are neutralized to a pH of about 7.0 to 7.5. The base employed for neutralization should be triethanolamine. Minimally, triethanolamine should be present at a ratio of 1/3 mole per mole of melamine; the rest of the neutralizing agent can be a base such as a solution o 5G% by weight sodium hydroxide.
It has been established that the total neutral-ization by soda yields resins not easily miscible in water and precipitation occurs due to the neutralization.
The purpose of neutralizing with triethanolamine is to Lmprove the water compatibility of the resin.
Fourth Stage - Stabilization - This stage of preparation of the resins of this invention is one in which the reacted mix is held at ele-vated temperatures of 50C to 90C, and preferably between 70C and 85C, for a period of time of about two to five hours. This holding period ~herein referred to as "sta-bilization") is important because it improves two proper-t~es of glass fiber mats held together with a binder pre-pared from the-aquc~us resin solutions. It has been found that increasing the duration of this stabilization stage 109i~36 . :~:
', '' ~-increases the flexibility index and stress resistance of the glass fiber mats.
The 1exibility index and stress resistance were determined in accordance with the following:
Sixty rectangular test pieces measuring 25 x S cm were cut from a glass fiber mat. On thirty of these test pieces, stress resistance was measured and the aver-age of these measurements taken.
The other thirty test pieces were each sub- -jected one time to folding under the following condi-tions. A metal plate was used which was 35 cm long and S cm wide, of 2 mm thickness, and supplied with two hin~es which permit folding it into two half-plates, each 12.5 cm long. Each flat mat test piece was placed ~ -on the unfolded plate and two other plates measuring 12.5 x S cm were applied over the mat~ The test piece was maintained tightly closed and flat between the plate supplied with hinges and the two half-plates completely folded 180 around the hinge. The distance between the two halves of the test pieces after folding was 10 mm, the test piece always being maintained between the plates, as described. The stress resistance of the thirty test pieces was measured and the average of these measurements taken. The loss of traction resistance after folding was then calculated in percentage.
The flexibility index is a numbcr on a scale of 0 to 10 which was determined in accordance with the following table:
, 1091~336 Loss of Stress Resistance Flexibility after Folding in % Index -0 to 4 10 4 to 10 10 to 20 8 20 to 30 7 3~ to 40 6 40 to 50 ~ 5 `
50 to 60 4 60 to 70 3 70 to 80 2 80 to gO
90 to 100 0 A ~mall lessening in percentage o~ free for-maldehyde of the aqueous resin solution and a gradual increase in its viscosity is observed during the stabil-ization stage. Since this may be detrimen~al to the shelf life of the resin solution, the stabilization is l~mited to the above-mentioned temperature ranges of 50C
to 90C, and preferably of 70C to 85C, for a period of time not to exceed two to five hours.
Under these conditions, the aqueous resin solution remains water compatible at a ratio of at least 12 times its volume.
If the duration of the stabilization period surpasses five hours, for the indicated temperature values, the resin acquires an undesirably high viscosity. If the 8tabilization is interrupted before two hours, the desired improvement in flexibility of glass fiber mats is not obtained.
.
Fifth Stage - Reduction of Free Formaldéhyde Th~ percentage of free formaldehyde of the aqueous rcsin solutions after the stabilization stage is even higher than the initial F/M ratio and is on the order of 6 to 12% or more. Such amounts of free formaldehyde are undesirable because, among other reasons, the vapors emitted during final curing irritate the eyes and respir-atory systems of the operators.
Thus, the principal objective of the fifth ,-~tage is to reduce the content of free formaldehyde to 6% or less. The irritating vapors emitted at these con-centrations are tolerable to the worker~.
Further, when the ~ormaldehyde content of the resin is reduced to 6~ or less, the stress re~istance o the resin-bonded glass fiber mats increases and the rate at which the viscosity of the stored aqueous resin solu-tions increases is minimized, thereby contributing to a prolonged shelf life.
The free formaldehyde content is reduced in the fifth phase by adding urea in a ratio of 0.6 to 1.6, and preferably 0.8 to 1.2 moles of urea per molc of melamine while the resin is heated to temperaturés as existed in the stabilization stage. The free formaldehyde content of the stabilized resin is a function of the initial F/M
ratio and therefore the molecular ratio of urea to mela-mine is referred to here as the U/M ratio.
.
109183~i EX~MPLE 1 Stage I
562 g of an aqueous solution o~ 36% formaldehyde and 0.5% methanol, 248 g of ethylene glycol and 49.5 g of triethanolamine were introduced into a one-liter reactor ~upplied with a reflux condenser, an agitator and a thermometer. The solution was heated to 65C and 126 g of melamine were added in twelve minutes during agitation.
The condensation reaction was continued at 65C until a cloud point of 50C was obtained, at which time the tem-. perature was rapidly lowered to 35C.
Stage II
, Etherification was commenced by adding 56 g of concentrated sulfuric acid over a thirty-minute period until a pH o 2 was reached. Etherification continued at 35C for one hour and thirty minutes.
Stage III
At the end of etherification, the p~ of the environment was adjusted to 7.2 by adding 49.5 g of tri-ethanolamine and 50 g of a 50% solution of sodium hydroxide.
- Stage IV
The temperature was then brought to 70C and the resin allowed to stabilize for five hours.
Stage V
At the end of five hours, 48 g of urea were introduced and the resin cooled to a temperature of about 60C.
- The rcsin obtained presented the following~
charactcristics:
. .
.. . . . . ..
1(~9~836 - :
- F/M ratio - 6.75 - P/M ratio ~ 4 - TEA/M - 0.33 - Number o molecules of triethanolamine, added after etherification, per molecule of melamine:
0.33 - U/M ratio = 0.8 - Dry extract: 50.1%
- Viscosity: 94 centipoise - -~
- Free formaldehyde: 1.9 - Water compatibility: infinite ~2,000) - pH: 7. 2 - After two months' storage: Infinite water com-patibility (~2,000) and a v~scosity of 160 cen-tipoise PreParation of S~zing An aqueous dispersion of starch paste was pre- -pared from potatoes, as modified by ethylene oxide treatment, having a concent~ation of 8% calculated in the form of anhydrous starch. Steam was bubbled in this dispersion until its temperature reached 98C and was -continued for twenty minutes. After cooling to 25-30C, the paste was ready to be used.
An aqueous solution of the preceding melaminé-formaldehyde resin corresponding to a dry weight of 1.2 kg was mixed with 110 Xg of the paste MLxed with the preceding mixture was an emul-sion of a homopolymer of polyvinyl acetate, which poly-vinyl acetate was plasticized by dibutyl phthalate to the extent of 50~ of plasticizer p~r weight of resin.
1.378 kg of a 58% emulsion, based on the dry weight of the plasticizcd homopolymcr~ was mixed with 1.378 kg (or an equal weight) of water and the resulting mixture added to the mixture of starch and melamine-formalde-hyde resin formed in the preceding step.
The diluted emuision was added to the preceding mix. The total was homogenized by agitation or ten minutes and constituted the concentrated sizing.
; When used, this concentrated sizing was diluted by a quantity of water such that the sizing finally used had a dry extract of 2.2%.
Preparation of a Glass Fiber Mat A mat of unbonded discontinuous glass fibers (hereinafter called "uncured mat") was used. This mat was obtained by distributina in regular fashion on a conveyor belt of metallic cloth discontinuous glass fibers obtained by steam attenuation of molten glass streams which flow from holes placed at the lower sec-tion of a platinum bushingO These glass fibers have an ~verage diameter of about 16 microns. The uncured ma~
used had a weight of 80~5g/m2.
The uncured mat, in the form of a continuous ribbon placed between two conveyor belts of metallic cloth, was immersed in the preceding prepared sizing.
The excess sizing retained by the uncured mat was extracted, always in a continuous fashion, by means of a bin with a depression placed below the lower belt.
The deprcssion was regulated in the bin so that the mat retained, after drying, 20~ by weight of dry binder in proportion to the total weigkt of glass and dry binder.
The uncured mat, sized and dried, was then con-109i83~
tinuously passed for two minutes in an air circulation ov~n heated to 145C.
The finished mat was found to have a stress resistance of 5.5 kg/cm and a flexibility index of 7.
A melamine-formaldehyde resin was prepared according to the operative mode of Example 1, using the following quantities of materials:
- formaldehyde at 36% 666 g - ethylene glycol 248 g :
- triethanolamine 49.5 g - melamine 126 g ~, - concentrated sulfuric acid 56 g ;
- aqueous solution of sod~um 50 g hydroxide at 50%
- urea 48 g ;
- triethanolamine 49.5 g The resin obtained had the following charac-teristics:
- 20 - F/M ratio: 8.0 - P/M ratio: 4.0 - TEA/M ratio: 0.33 - Number of molecules of triethanolamine, added after etherification, per molecule of melamine:
0.33 - U/M: 0.8 - Dry.extract: 47.8%
- - Viscosity: 70 centipoise . - Free forma~dchyde: 4.0~
, - Water compatibility: infinite ~2,000) - pH: 7.2 , lOgl83~ " `, - After two months' storage: Infinite water com-patibility (~2,000) and a ~iscosity of 130 centipoise.
By u~ing the preceding resin, a paste was pre-pared that was applied on the uncured mat which was then dried in an oven according to the method described in Example 1.
The stress resistance of the final mat was 5.6 kg/cm and the flexibility index was 7.
EXAMPLE 3 f A melamine-formaldehyde resin was prepared according to the method of Example 1, using the quan-t~ties of materials set forth below:
- ~ormaldehyde at 36% 750 g - ethylene glycol 248 g - triethanolamine 49.5 g - melamine 126 g - concentrated s~lfuric acid 5~ g .
- triethanolamine 49.5 g - aqueous solution of sodium 50 g hydroxide at 50%
- .urea 48 g The characteristics of this resin were as fol-lows: .
- F/M ratio: 9.0 - P/M ratio: 4.0 - TEA/M ratio: 0.33 - Number of triethanolamine moleculesJ added after etherification, per molecule of melamine: 0.33 3n U/M ratio: 0.8 - Dry extract: 45.6%
109183~
- Viscosity: 52 centipoise - Free formaldehyde: 5.4%
- Water compatibility: infinite (~2,000) _ p~ 7.2 - After two months' storage: In~inite water com-patibility ~2,000) and a viscosity of 100 cen-tipoise.
By using the preceding resin, a sizing was prepared th~t was applied to the uncured mat which was then dried in an oven according to the method described in Example 1.
Ths finished mat had a stress resistance of 5.9 ~g/cm and a flexibility index of 8.
~XAMPLE 4 . A formaldehyae-melamine resin was prepared -:
according to the method of Example 1, using the follow-ing quantities of materials:
- formaldehyde at 36~ 6b6.5 g - ethylene glycol 198.5 g - triethanolamine 39.5 g - melamine 101.0 g - concentrated sulfuric acid45.0 g - triethanolamine 39.5 g - aqueous solution of sodium40.0 g hydroxide at 50% .
urea 38.5 g The characteristics of this resin were as fol-lows: ~ -- F/M ratio: 10.0 - P/M ratio: 4.0 - TEA/M ratio: 0.33 .
, - Number of triethanolamine molecules, added aftcr ethexification, per molecule of melamine: 0.33 - U/M ratio: 0.8 - Dry extract: 43.2%
- Viscosity: 44 centipoise - Free formaldehyde: 5.7 - Water compatibility: infinite (~2,000) - pH: 7.2 , - After two months' storage: Infinite water com-- - patibility (~2,000) and a viscosity of 92 cen-tipoise.
A sizing was prepared by using the preceding resin and then a mat manufactured according to the method of Example 1. This mat had a stress resistance o~ 6.2 kg/cm and a ~lexibility index o~ 7.
. * * *
If the stress resistances of the mats obtained in Examples 1, 2, 3 and 4 are compared, the relationshi~ -between a rise in stress resistance with increasing F/M
, . .
ratios can be seen.
Stress Resis-Example F/M Ratio tance (kg/cm) 1 6~75 5.5 ,
2 8.0 5.6
3 9.0 5.9
4 ------ - 10.0 - 6.2 An alkaline condensation with formaldehyde and ~e~amine was conducted in a reaction vessel at 65C with vigorou~ .ag~a~ion,.using the following quantities of mater-ia~s~
~091836 ` ::
- ethylene glycol 248 g (4 mol.) - tricthanolamine 49.5 g ~0.33 mol.) - melamine 126 g (1 mol.) - formaldehyde see below ~ he aqueous solution of formaldehyde at 36%
containing 0. 5% methanol was placed in a reactor.
Glycol and triethanolamine were added and the mixture heated to reaction temperature. The melamine was then added in twelve minutes. ;~
, 10 For i~creasing quantities of agueous formalde-hyde solutions, the following determinations were made: -- P/M ratio 2.5 - Even after three hours at 65C, the reacting en~ironment remained cloudy. Continuous heating resulted in solidification of the resin. ~ -- F/M ratio 2.9 - At the end of ninety minutes at 65C, the reacting mixture was clear. Operations were continued corresponding to ~tages 2-5 according~to the conditions indicated in Example 1. The final resin had no water compatibility.
- F/~ ratio 4.0 - The reacting environment of the alkaline condensation became clear after fifty minutes at 65C. Preparation was finished according to the method of Example 1. Tne resin obtained had a water compatibility of only 1,000.
A sizing was prepared with the last resin and a glass fiber mat manufactured according to the methods of Example 1. The stress resistance of this mat was only 4.2 ~g/cm This example shows that the d~sadvantageous .
~ - 22 -1091~36 . ~:
.
results of an F/M ratio < 5.0 are lack of desired wa-ter co~patibility of the resins and weakening of the stress resistance of the glass fiber mat.
E%AMPLE 6 Three resins were prepared according to the conditions indicated in Example 1, except that the cloud point was 12C for all the preparations. Further, the temperature of alkaline condensation was varied ;
from one preparation to the other. The following results were obtained:
First Preparation Condensàtion at a temperature of 60C for forty-fl~e minutes, The resin had a viscos~ty of 14 cent~poise and a water compatibility higher than 2,000.
Second Preparation Condensation at a temperature of 65C for thirty-five minutes, The resin had a viscosity~of 12 centipoise and a water compatibility higher than 2,000.
Third Preparation Condensation at a temperature of 70C for twenty-three minutes. The resin had a viscosity of 11 centipoise and a water compatibility higher than 2,000.
However, at the end of only fifteen days' storage, these three resins had such increased viscosi-ties that they had the consistency of a gel.
This example shows the necessity of a sufficiently high cloud point in order to obtain a good shelf life of the resins. One should also note, by comparison with Example 1, that the viscosity is reduced when the ~ .
-temperature of the cloud point is lowered.
EXAMPLE 7 i.
A melamine-formaldehyde resin was prepared according to the method of Example 4, using the follow-ing quantities of material:
- formaldehyde 665.5 g - ethylene glycol 198.5 g - triethanolamine 39.5 g - melamine 101.0 g ,10 - concentrated sulfuric acid 45.0 g , - triethanolamine 39i5 g ~ .
- aqueous solution of sodium 40.0 g hydroxide at 50% . .
- ur~a 57.5 g The method was varied from that of Example 4 in that the alkaline condensation was continued to a cloud point of 62C instead of 50C, in that the time ~therification duration was increased to three hours and ten minutes instead of two hours, and in that the stabilization phase was altered to three hours at 85C
instead of five hours at 70C.
~ he characteristics of this resin were the same as those of the resin of Example 4 except for the following: -- U~M ratio: 1.2 - Dry extract: 43.3%
- Viscosity: ~0 centipoise - Free formaldehyde: 4.5%
- Water compatibility: 1,900 , . .
~091836 - After two months' storage: Water compatibility ~ -was 1,400 and viscosity was 210 centipoise.
A ~i~ing was prepared with the preceding resin and the method of Example 1 used to manufacture a mat. -~
The mat had a stress resistance of 6.7 kg/cm and a flexibility index of 6.
This example shows the possibility of prepar-ing a resin according to the invention by stopping the alkaline condensation at a cloud point of 62C. It further shows that the total etherification duration should be adjusted in function of the cloud point value.
A resin was prepared according to Example 4 except that a TEA/M ratio of 0.1 instead of 0.33 was u~d at the time of the alkaline condensation.
The obtained resin had practically no water compatibility (~50) and a viscosity of 275 centipoise.
, This example illustrates, by comparison with Example 4, the disadvantage of using, at the time of alkaline condensation, a TEA/M ratio that is too low, and also illustrates the importance of the role of tri-ethanolamine in imparting ~ood viscosity and high water compatibility to the resin.
A resin was prepared according to the method of Example 4, but sodium hydroxide was used as catalyst for the alkaline condensation instead of triethanolamine.
The quantities of materials used were as follows:
- formaldehyde at 36% 666.5 g (8 mol.) ~09i836 - ethylene glycol 198.5 g t3.2 mol.) - S0~ agueous solution of 1 ml sodium hydroxide - melamine 101 g ~0.8 mol.) - concentrated sulfuric acid 10 ml - triethanolamine 39.5 g (0.264 mol.) ~ .
- 50% aqueous solution of 7 ml sodium hydroxide The resin obtained after the etherification 10 phàse and neutralization had practically no water com- :
patibility ~ 100). If the resin is stabilized by heat-ing under the conditions of Example 4, it is transformed into a gel.
Thi example shows, as did Example 8, the ' .
important role o the triethanolamine introduction during the alkaline condensation phase. This introduc-tion of triethanolamine results in good viscosity and suitable water compatibility which canno,t be obtained with sodium hydroxiae.
This example illustrates the use of a certain variety of different polyols based on ethylene glycol in the synthesis of the resins of the present invention.
The preparations are made according to all the conditions described in Example 1, except for the nature ,-and ~uantities of polyols and for certain particulari-ties for each polyol which are indicated in the follo~-~ng table: .
.
Nature & Quantity . Results and of polY ~ mol Particu].arities Observations Glycerol: 4 mol 3 hr. stabiliza- Water compat-tion at 75C ibility: 2,000 . IStage IV) . Viscosity:
- - - 90 centipoise :
Stable 2 months' storage 10 Diethyleneglycol: Water compati-.4 mol bility: 2,000 - Viscosity:
94 centipoise Stable 2 months' storage . .
d-gluco~e: 0.4 Cloud point of Water compati--47C obtained bility: 2,.~00 Ethylene glycol 3.0 ater 70 minutes -at 65C ~Stage I) Viscosity:
112 centipoise Stable 2 months' storage Triethylene glycol Cloud point o Water compati-4 mol 47C obtained bility: 2,000 after 120 min-utes at 65C Viscosity:
(Stage I) 98 centipoise -~
Stable 2 - months' storage . Three melamine-formaldehyde resins were pre-pared according to the general method of ~le preceding examples, using the following quantities of matérials:
formaldehyde at 36% 583O3 g (7 mol) - triethanolamine 4~.5 g ~0.33 mol) - melamine 126.0 g ll mol) 1(~91836 `
- concentrated sulfuric acid 56.0 g - triethanolamine 49.5 g (0.33 mol) - 50% aqueous solution of 50.0 g .
sodium hydroxide - urea 48.0 g (0.8 mol) ~`
The alkaline condensations were made at 65C~:
and discontinued at a cloud point of 52C. The etheri-fications were made at a pH of 2 and a temperature of 30C.
These three preparations differ by the mix of polyols used: -~
Preparations Mix of Polyol A B C
Sucrose ~saccharose) 342 g 171 g 86 g Ethylens glycol 0 124 g 186 g Resin A was etheri~ied only forty minutes bQcause its viscosity was already very high. Resins - s B and C were etherified for a total period of ninety minutes.
After neutralization, the three preparations were stabilized for five hours at 70C. 95 g of water had to be added to Resin A during heating because of its thickness.
The characteristics of the resins finally obtained were as follows~
'A - B C
F/M ratio 7.0 7.0 . 7.0 Molecular ratio:
Sucrose/melamine 1.0' 0.5 0.25 Ethylene glycol/ 2.0 3.0 melamine TEA~M ratio 0.33 0.33 0-33 - 28 - .
8:~6 -:
A B C
Number of molecules of 0.33 0.33 0,33 triethanolamine added after ctherification, per molecule of melamine U/M ratio 0.8 0.8 0.8 Dry extxact (~) 57.3* 55.6 54.0 ~*includes water added during stabilization) Vlscosity in centipoise 2,100 1,100 125 Water compatibility 1,800 2,000 2,000 This example illustrates the possibility of obtaining resins of viscosities that are very different and that can be regulated as desired by adding varying r~lative proportions of sucrose and ethylene glycol.
In ~stablishing the relative proportions of the two polyols in the threè r~sins, A, B and C, above, it wa~, considered that the sucrose, including eight hydroxyl alcoholic groups per molecule, should be employed in molecular ~uantities four times less than the diol.
Finally, it is evid~nt that only low portions of sucrose - can furnish useful resins for general practice.
ExAMæLE 12 Three resins were prepared according to Example 1 except for the quantities of ethylene glycol.
Resin A was prepared using a P/M ratio of 2Ø
During the etherification phase; a solidifying of the resin was observed which could not be stabilized by the addition of water.
Resin B was prepared using a P/M ratio of 2.5.
There was no solidification during etheriflcation, but the final resin had a water compatibility of only 1,000.
.
i09~:836 .
~ sin C was prepared using a P/M ratio of 3Ø
No difficulty was encountered in the prepaxation of thi~ resin ~nd an infinite water compatibility (~2,000) was obtained.
This example shows the necessity of using a P/M ratio of at least 3.0 in order to obtain good water compatibility.
EXAMPLE 13 ~;
Two resins were prepared under the conditionc~
, 10 described in Example 1, except those concerning pH and temperature of the etherification phase.
Etherification of Resin A took place at a pH
of 4 and a temperature of 40C. The obtained resin pre~entea normal viscosity and water compatibility the day after its manufacture. However, twenty days later, the viscosity of the resin had no increased that it was a type of gel at ambient temperature.
Etherification of Resin B took place at a pH
of l.S and a temperature of 20C. The day after its manufacture, the resin presented a water compatibility higher than 2,000 and a viscosity of 15 centipoise.
After two months' storage, the water compatibility was hlgher than 2,000 and the viscosity was 40 centipoise.
A sizing was prepared with Resin B and a glass fiber mat manufactured according to the specifications of Example 1. Stress resistance for the mat was only 4.0 kg/cm.
By comparison with the results indicated in Example 1, the present example shows the disadvantages 1091836 .
encountered if one departs from the defined pH and temperature values during the etherification stage.
Two resins wcre prepared according to the specifications of Example 4, except for the duration of the etherification phase.
Resin A - The total duration of etherifica-tion, acid flow included, was only sixty minutes for a cloud point of 50C instead of ninety minutes for this same cloud point. The final viscosity of the resin was only 23 centipoise, and its water compati-billty was higher than 2,000 A ~izing was pxepaxed with Resin A and a glass fiber mat manufactured according to Example 1.
The stress resistance of the mat was only 4.9 kg/cm.
Resin B - The total duration of etherifica-tion was prolonged to 180 minutes for a cloud point which is always 50C. The resin obtained presented a viscosity of 285 centipoise and a water compatibility of 1,500. After two months' storage, viscosity of Resin B was 1,050 centipoise and water compatibility was 600.
This example shows, by comparison with the xesults of Example 4, the disadvantages encountered ~n not conforming, for the etherification reaction, to the limits indicated for its total duration for a given cloud point.
~XAMPLE i5 A resin was preparcd according to Example 4, 10~1~36 .
except that 60 g of aqucous solution of hydrochloric acid at 35.5% were used instead of 45 g of concentrated ~ulfuric acid.
The characteristics of this resin, apart from the molecular ratios of the different reactors which are those of Example 4, were:
- Dry extract: 43.3% . ---- Viscosity: 35 centipoise - ~ree formaldehyde: 5.5% 0 . - Water compatibility: infinite ( 2,000) -- Viscosity: 30 centipoise - - -- After two months' storage: Infinite water com-patibility ~72,000) and a viscosity of 55 centi-poise.
~ A 5i21ng was prepared with this resin and a mat manufactured in accordance with the specifications of Example 1. The m~t was found to have a stress resis-tance of 6.0 kg~cm ana a flexibility index of 7.
Analogous results are obtained wit~ orthophos-phoric, nitric, formic or monochloracetic acids if thesame methods and stoichiometric proportions are used.
This example shows that various acids can be used interchangeably in the practice of the present ~nvention.
EXAMPL~ 16 A resin was prepared according to Example 4, cxcept that ne~tralization was effected--to a p~I of 7.2 ~fter eth~ri~ication solely by an aqueous solution of .
50% sodium hydroxide instëad:of-using 0.33 mol. of tri-ethanolamine and 40 g of 50% aqueous solution of sodium - 3i -lO~i836 hydroxide. During stabilization at 70C ~Stage IV), ~olidif~cation of the resin occurs after two hours.
This resin cannot be solubilized by the addition of watex.
This example shows the necessity of using, at least in part, triethanolamine for the neutraliza-tion of the resin after the etherification phase. It shows, in comparison with Example 8 and 9, that tri-ethanolamine plays an essential role in obtaining water compatibility, not only during Stage I (catalyst of the alkaline condensation), but also at the end of Stage II ~etherification~ at the time of its neutrali-zation.
l'hls example shows the improvements obtained by stabilization (Stage IV).
Four resins were prepared according to Example 1, exc~pt that the etherification temperature was 30C
for all preparations instead of 35C.
Duration of the stabilization phase (Stage IV) was varied by increasing it from one preparation to the next.
With each resin, a sizing was prepared and a glass fiber mat manufactured according to Example 1.
~he results obtained are set forth in the fol-lowing table: ' 1~183~;
-ST~BILIZATION
Nonë ---I hour 4 hours 5 hours ~tress resistance 4.2 4.6 4.8 of glass fiber mats ~n kg/cm Flexibility index S 6 8 o glass fiber mats Viscosity of aqueous 41 53 115 245 This example shows the very rapid increase in 10 viscosity after about four hours of stabilization and demonstrates that the duration of stabilization must be limited in order to obtain usable resins.
This example illustrates the improvements obtained by the addition of urea to the resins after the stabilization phase.
A resin was prepared according to Example 4, but no urea was added at the end of manufacture. A
sizing was prepared from the resin and a glass fiber mat manufactured according to Example 1.
In the following table, the results obtained are compared to the results of Example 4:
Resin ofResin with Example 4No Urea Free formal~ehyde (%) 5.7 11.0 Stress resistance of glass 6.2 . 5.7 fiber mat in ~g/cm Viscosity after manufacture 44 . 55 in cen ipoise Viscosity two months after 92 185 manufacture in centipoise * .
i4 -The resins of the instant invention are advan-tag~ous for binding mats of thin glass fibers, particu-larly those of a thickness less than 4 mm. The resins ~mpart good qualities of flexibility and stress resis-tance.
~091836 ` ::
- ethylene glycol 248 g (4 mol.) - tricthanolamine 49.5 g ~0.33 mol.) - melamine 126 g (1 mol.) - formaldehyde see below ~ he aqueous solution of formaldehyde at 36%
containing 0. 5% methanol was placed in a reactor.
Glycol and triethanolamine were added and the mixture heated to reaction temperature. The melamine was then added in twelve minutes. ;~
, 10 For i~creasing quantities of agueous formalde-hyde solutions, the following determinations were made: -- P/M ratio 2.5 - Even after three hours at 65C, the reacting en~ironment remained cloudy. Continuous heating resulted in solidification of the resin. ~ -- F/M ratio 2.9 - At the end of ninety minutes at 65C, the reacting mixture was clear. Operations were continued corresponding to ~tages 2-5 according~to the conditions indicated in Example 1. The final resin had no water compatibility.
- F/~ ratio 4.0 - The reacting environment of the alkaline condensation became clear after fifty minutes at 65C. Preparation was finished according to the method of Example 1. Tne resin obtained had a water compatibility of only 1,000.
A sizing was prepared with the last resin and a glass fiber mat manufactured according to the methods of Example 1. The stress resistance of this mat was only 4.2 ~g/cm This example shows that the d~sadvantageous .
~ - 22 -1091~36 . ~:
.
results of an F/M ratio < 5.0 are lack of desired wa-ter co~patibility of the resins and weakening of the stress resistance of the glass fiber mat.
E%AMPLE 6 Three resins were prepared according to the conditions indicated in Example 1, except that the cloud point was 12C for all the preparations. Further, the temperature of alkaline condensation was varied ;
from one preparation to the other. The following results were obtained:
First Preparation Condensàtion at a temperature of 60C for forty-fl~e minutes, The resin had a viscos~ty of 14 cent~poise and a water compatibility higher than 2,000.
Second Preparation Condensation at a temperature of 65C for thirty-five minutes, The resin had a viscosity~of 12 centipoise and a water compatibility higher than 2,000.
Third Preparation Condensation at a temperature of 70C for twenty-three minutes. The resin had a viscosity of 11 centipoise and a water compatibility higher than 2,000.
However, at the end of only fifteen days' storage, these three resins had such increased viscosi-ties that they had the consistency of a gel.
This example shows the necessity of a sufficiently high cloud point in order to obtain a good shelf life of the resins. One should also note, by comparison with Example 1, that the viscosity is reduced when the ~ .
-temperature of the cloud point is lowered.
EXAMPLE 7 i.
A melamine-formaldehyde resin was prepared according to the method of Example 4, using the follow-ing quantities of material:
- formaldehyde 665.5 g - ethylene glycol 198.5 g - triethanolamine 39.5 g - melamine 101.0 g ,10 - concentrated sulfuric acid 45.0 g , - triethanolamine 39i5 g ~ .
- aqueous solution of sodium 40.0 g hydroxide at 50% . .
- ur~a 57.5 g The method was varied from that of Example 4 in that the alkaline condensation was continued to a cloud point of 62C instead of 50C, in that the time ~therification duration was increased to three hours and ten minutes instead of two hours, and in that the stabilization phase was altered to three hours at 85C
instead of five hours at 70C.
~ he characteristics of this resin were the same as those of the resin of Example 4 except for the following: -- U~M ratio: 1.2 - Dry extract: 43.3%
- Viscosity: ~0 centipoise - Free formaldehyde: 4.5%
- Water compatibility: 1,900 , . .
~091836 - After two months' storage: Water compatibility ~ -was 1,400 and viscosity was 210 centipoise.
A ~i~ing was prepared with the preceding resin and the method of Example 1 used to manufacture a mat. -~
The mat had a stress resistance of 6.7 kg/cm and a flexibility index of 6.
This example shows the possibility of prepar-ing a resin according to the invention by stopping the alkaline condensation at a cloud point of 62C. It further shows that the total etherification duration should be adjusted in function of the cloud point value.
A resin was prepared according to Example 4 except that a TEA/M ratio of 0.1 instead of 0.33 was u~d at the time of the alkaline condensation.
The obtained resin had practically no water compatibility (~50) and a viscosity of 275 centipoise.
, This example illustrates, by comparison with Example 4, the disadvantage of using, at the time of alkaline condensation, a TEA/M ratio that is too low, and also illustrates the importance of the role of tri-ethanolamine in imparting ~ood viscosity and high water compatibility to the resin.
A resin was prepared according to the method of Example 4, but sodium hydroxide was used as catalyst for the alkaline condensation instead of triethanolamine.
The quantities of materials used were as follows:
- formaldehyde at 36% 666.5 g (8 mol.) ~09i836 - ethylene glycol 198.5 g t3.2 mol.) - S0~ agueous solution of 1 ml sodium hydroxide - melamine 101 g ~0.8 mol.) - concentrated sulfuric acid 10 ml - triethanolamine 39.5 g (0.264 mol.) ~ .
- 50% aqueous solution of 7 ml sodium hydroxide The resin obtained after the etherification 10 phàse and neutralization had practically no water com- :
patibility ~ 100). If the resin is stabilized by heat-ing under the conditions of Example 4, it is transformed into a gel.
Thi example shows, as did Example 8, the ' .
important role o the triethanolamine introduction during the alkaline condensation phase. This introduc-tion of triethanolamine results in good viscosity and suitable water compatibility which canno,t be obtained with sodium hydroxiae.
This example illustrates the use of a certain variety of different polyols based on ethylene glycol in the synthesis of the resins of the present invention.
The preparations are made according to all the conditions described in Example 1, except for the nature ,-and ~uantities of polyols and for certain particulari-ties for each polyol which are indicated in the follo~-~ng table: .
.
Nature & Quantity . Results and of polY ~ mol Particu].arities Observations Glycerol: 4 mol 3 hr. stabiliza- Water compat-tion at 75C ibility: 2,000 . IStage IV) . Viscosity:
- - - 90 centipoise :
Stable 2 months' storage 10 Diethyleneglycol: Water compati-.4 mol bility: 2,000 - Viscosity:
94 centipoise Stable 2 months' storage . .
d-gluco~e: 0.4 Cloud point of Water compati--47C obtained bility: 2,.~00 Ethylene glycol 3.0 ater 70 minutes -at 65C ~Stage I) Viscosity:
112 centipoise Stable 2 months' storage Triethylene glycol Cloud point o Water compati-4 mol 47C obtained bility: 2,000 after 120 min-utes at 65C Viscosity:
(Stage I) 98 centipoise -~
Stable 2 - months' storage . Three melamine-formaldehyde resins were pre-pared according to the general method of ~le preceding examples, using the following quantities of matérials:
formaldehyde at 36% 583O3 g (7 mol) - triethanolamine 4~.5 g ~0.33 mol) - melamine 126.0 g ll mol) 1(~91836 `
- concentrated sulfuric acid 56.0 g - triethanolamine 49.5 g (0.33 mol) - 50% aqueous solution of 50.0 g .
sodium hydroxide - urea 48.0 g (0.8 mol) ~`
The alkaline condensations were made at 65C~:
and discontinued at a cloud point of 52C. The etheri-fications were made at a pH of 2 and a temperature of 30C.
These three preparations differ by the mix of polyols used: -~
Preparations Mix of Polyol A B C
Sucrose ~saccharose) 342 g 171 g 86 g Ethylens glycol 0 124 g 186 g Resin A was etheri~ied only forty minutes bQcause its viscosity was already very high. Resins - s B and C were etherified for a total period of ninety minutes.
After neutralization, the three preparations were stabilized for five hours at 70C. 95 g of water had to be added to Resin A during heating because of its thickness.
The characteristics of the resins finally obtained were as follows~
'A - B C
F/M ratio 7.0 7.0 . 7.0 Molecular ratio:
Sucrose/melamine 1.0' 0.5 0.25 Ethylene glycol/ 2.0 3.0 melamine TEA~M ratio 0.33 0.33 0-33 - 28 - .
8:~6 -:
A B C
Number of molecules of 0.33 0.33 0,33 triethanolamine added after ctherification, per molecule of melamine U/M ratio 0.8 0.8 0.8 Dry extxact (~) 57.3* 55.6 54.0 ~*includes water added during stabilization) Vlscosity in centipoise 2,100 1,100 125 Water compatibility 1,800 2,000 2,000 This example illustrates the possibility of obtaining resins of viscosities that are very different and that can be regulated as desired by adding varying r~lative proportions of sucrose and ethylene glycol.
In ~stablishing the relative proportions of the two polyols in the threè r~sins, A, B and C, above, it wa~, considered that the sucrose, including eight hydroxyl alcoholic groups per molecule, should be employed in molecular ~uantities four times less than the diol.
Finally, it is evid~nt that only low portions of sucrose - can furnish useful resins for general practice.
ExAMæLE 12 Three resins were prepared according to Example 1 except for the quantities of ethylene glycol.
Resin A was prepared using a P/M ratio of 2Ø
During the etherification phase; a solidifying of the resin was observed which could not be stabilized by the addition of water.
Resin B was prepared using a P/M ratio of 2.5.
There was no solidification during etheriflcation, but the final resin had a water compatibility of only 1,000.
.
i09~:836 .
~ sin C was prepared using a P/M ratio of 3Ø
No difficulty was encountered in the prepaxation of thi~ resin ~nd an infinite water compatibility (~2,000) was obtained.
This example shows the necessity of using a P/M ratio of at least 3.0 in order to obtain good water compatibility.
EXAMPLE 13 ~;
Two resins were prepared under the conditionc~
, 10 described in Example 1, except those concerning pH and temperature of the etherification phase.
Etherification of Resin A took place at a pH
of 4 and a temperature of 40C. The obtained resin pre~entea normal viscosity and water compatibility the day after its manufacture. However, twenty days later, the viscosity of the resin had no increased that it was a type of gel at ambient temperature.
Etherification of Resin B took place at a pH
of l.S and a temperature of 20C. The day after its manufacture, the resin presented a water compatibility higher than 2,000 and a viscosity of 15 centipoise.
After two months' storage, the water compatibility was hlgher than 2,000 and the viscosity was 40 centipoise.
A sizing was prepared with Resin B and a glass fiber mat manufactured according to the specifications of Example 1. Stress resistance for the mat was only 4.0 kg/cm.
By comparison with the results indicated in Example 1, the present example shows the disadvantages 1091836 .
encountered if one departs from the defined pH and temperature values during the etherification stage.
Two resins wcre prepared according to the specifications of Example 4, except for the duration of the etherification phase.
Resin A - The total duration of etherifica-tion, acid flow included, was only sixty minutes for a cloud point of 50C instead of ninety minutes for this same cloud point. The final viscosity of the resin was only 23 centipoise, and its water compati-billty was higher than 2,000 A ~izing was pxepaxed with Resin A and a glass fiber mat manufactured according to Example 1.
The stress resistance of the mat was only 4.9 kg/cm.
Resin B - The total duration of etherifica-tion was prolonged to 180 minutes for a cloud point which is always 50C. The resin obtained presented a viscosity of 285 centipoise and a water compatibility of 1,500. After two months' storage, viscosity of Resin B was 1,050 centipoise and water compatibility was 600.
This example shows, by comparison with the xesults of Example 4, the disadvantages encountered ~n not conforming, for the etherification reaction, to the limits indicated for its total duration for a given cloud point.
~XAMPLE i5 A resin was preparcd according to Example 4, 10~1~36 .
except that 60 g of aqucous solution of hydrochloric acid at 35.5% were used instead of 45 g of concentrated ~ulfuric acid.
The characteristics of this resin, apart from the molecular ratios of the different reactors which are those of Example 4, were:
- Dry extract: 43.3% . ---- Viscosity: 35 centipoise - ~ree formaldehyde: 5.5% 0 . - Water compatibility: infinite ( 2,000) -- Viscosity: 30 centipoise - - -- After two months' storage: Infinite water com-patibility ~72,000) and a viscosity of 55 centi-poise.
~ A 5i21ng was prepared with this resin and a mat manufactured in accordance with the specifications of Example 1. The m~t was found to have a stress resis-tance of 6.0 kg~cm ana a flexibility index of 7.
Analogous results are obtained wit~ orthophos-phoric, nitric, formic or monochloracetic acids if thesame methods and stoichiometric proportions are used.
This example shows that various acids can be used interchangeably in the practice of the present ~nvention.
EXAMPL~ 16 A resin was prepared according to Example 4, cxcept that ne~tralization was effected--to a p~I of 7.2 ~fter eth~ri~ication solely by an aqueous solution of .
50% sodium hydroxide instëad:of-using 0.33 mol. of tri-ethanolamine and 40 g of 50% aqueous solution of sodium - 3i -lO~i836 hydroxide. During stabilization at 70C ~Stage IV), ~olidif~cation of the resin occurs after two hours.
This resin cannot be solubilized by the addition of watex.
This example shows the necessity of using, at least in part, triethanolamine for the neutraliza-tion of the resin after the etherification phase. It shows, in comparison with Example 8 and 9, that tri-ethanolamine plays an essential role in obtaining water compatibility, not only during Stage I (catalyst of the alkaline condensation), but also at the end of Stage II ~etherification~ at the time of its neutrali-zation.
l'hls example shows the improvements obtained by stabilization (Stage IV).
Four resins were prepared according to Example 1, exc~pt that the etherification temperature was 30C
for all preparations instead of 35C.
Duration of the stabilization phase (Stage IV) was varied by increasing it from one preparation to the next.
With each resin, a sizing was prepared and a glass fiber mat manufactured according to Example 1.
~he results obtained are set forth in the fol-lowing table: ' 1~183~;
-ST~BILIZATION
Nonë ---I hour 4 hours 5 hours ~tress resistance 4.2 4.6 4.8 of glass fiber mats ~n kg/cm Flexibility index S 6 8 o glass fiber mats Viscosity of aqueous 41 53 115 245 This example shows the very rapid increase in 10 viscosity after about four hours of stabilization and demonstrates that the duration of stabilization must be limited in order to obtain usable resins.
This example illustrates the improvements obtained by the addition of urea to the resins after the stabilization phase.
A resin was prepared according to Example 4, but no urea was added at the end of manufacture. A
sizing was prepared from the resin and a glass fiber mat manufactured according to Example 1.
In the following table, the results obtained are compared to the results of Example 4:
Resin ofResin with Example 4No Urea Free formal~ehyde (%) 5.7 11.0 Stress resistance of glass 6.2 . 5.7 fiber mat in ~g/cm Viscosity after manufacture 44 . 55 in cen ipoise Viscosity two months after 92 185 manufacture in centipoise * .
i4 -The resins of the instant invention are advan-tag~ous for binding mats of thin glass fibers, particu-larly those of a thickness less than 4 mm. The resins ~mpart good qualities of flexibility and stress resis-tance.
Claims (36)
1. A process for preparing a solution of melamine-formaldehyde resin etherified by condensation in alkaline solution of formaldehyde and melamine followed by an etherifi-cation, comprising the steps of:
a) adding melamine to a solution of between 30% and 50% formaldehyde in the presence of a polyol and triethanol-amine and at a temperature of between 60° and 70° C, the formaldehyde/melamine molar ratio being between 5 and 11, the polyol/melamine molar ratio being between 3 and 5 and the triethanolamine/melamine molar ratio being between 0.2 and 0.6;
b) terminating the condensation reaction when a cloud point appears at between 40°C and 65°C for the reactant solution, this termination carried out by cooling to a temperature between 20°C and 40°C;
c) etherifying the aqueous condensate solution by acidifying the solution while maintaining the temperature thereof between 20°C and 40°C.
d) terminating the etherification by neutralizing the cooled acidic solution with a base that includes triethanol-amine of a molar ratio of at least one-third molecule per molecule of melamine; and e) stabilizing the neutralized solution by maintaining it at a temperature of between 50°C and 90°C.
a) adding melamine to a solution of between 30% and 50% formaldehyde in the presence of a polyol and triethanol-amine and at a temperature of between 60° and 70° C, the formaldehyde/melamine molar ratio being between 5 and 11, the polyol/melamine molar ratio being between 3 and 5 and the triethanolamine/melamine molar ratio being between 0.2 and 0.6;
b) terminating the condensation reaction when a cloud point appears at between 40°C and 65°C for the reactant solution, this termination carried out by cooling to a temperature between 20°C and 40°C;
c) etherifying the aqueous condensate solution by acidifying the solution while maintaining the temperature thereof between 20°C and 40°C.
d) terminating the etherification by neutralizing the cooled acidic solution with a base that includes triethanol-amine of a molar ratio of at least one-third molecule per molecule of melamine; and e) stabilizing the neutralized solution by maintaining it at a temperature of between 50°C and 90°C.
2. A process for the preparation of an etherified melamine-formaldehyde resin comprising the sequential steps of:
a) adding melamine to an alkaline solution of between 30% and 50% formaldehyde in the presence of a polyol and triethanolamine and at a temperature of between 60°C and 70°C, the formaldehyde/melamine molar ratio being between 5 and 11, the polyol/melamine molar ratio being between 3 and 5, and the triethanolamine/melamine ratio being between 0.2 and 0.6;
b) terminating the condensation reaction when a cloud point appears at between 40°C to 65°C for the reactant solution, this termination carried out by cooling to a temperature between 20 C and 40 C;
c) etherifying the aqueous condensate solution by acidifying the solution to a pH between 1.5 and 3 while main-taining the temperature thereof between about 25°C to about 40°C;
d) terminating the etherification by neutralizing the cooled acidic solution with a base that includes triethanol-amine in a molar ratio of at least one part triethanolamine to three parts melamine.
e) stabilizing the neutralized solution by heating it to a temperature between about 50°C to about 90°C for a period of time in excess of about 2 hours; and f) reducing the free formaldehyde content of the stabilized solution to less than 6%.
a) adding melamine to an alkaline solution of between 30% and 50% formaldehyde in the presence of a polyol and triethanolamine and at a temperature of between 60°C and 70°C, the formaldehyde/melamine molar ratio being between 5 and 11, the polyol/melamine molar ratio being between 3 and 5, and the triethanolamine/melamine ratio being between 0.2 and 0.6;
b) terminating the condensation reaction when a cloud point appears at between 40°C to 65°C for the reactant solution, this termination carried out by cooling to a temperature between 20 C and 40 C;
c) etherifying the aqueous condensate solution by acidifying the solution to a pH between 1.5 and 3 while main-taining the temperature thereof between about 25°C to about 40°C;
d) terminating the etherification by neutralizing the cooled acidic solution with a base that includes triethanol-amine in a molar ratio of at least one part triethanolamine to three parts melamine.
e) stabilizing the neutralized solution by heating it to a temperature between about 50°C to about 90°C for a period of time in excess of about 2 hours; and f) reducing the free formaldehyde content of the stabilized solution to less than 6%.
3. A process according to claim 1 additionally comprising the step of reducing the free formaldehyde content of the stabilized solution by the addition of urea.
4. A process according to claim 2 wherein the formal-dehyde/melamine molar ratio is between 6.5 and 10.
5. A process according to claim 2 wherein the polyol/
melamine molar ratio is between 3.5 and 4.
melamine molar ratio is between 3.5 and 4.
6. A process according to claim 2 wherein the tri-ethanolamine/melamine molar ratio is between 0.3 and 0.5.
7. A process according to claim 2 wherein the condens-ation reaction is conducted with a formaldehyde solution of 34% to 38% and at a pH of between about 8.5 and 9.5.
8. A process according to claim 7 wherein the temperature is between 63°C and 68°C and the pH is between 8.8 and 9.2.
9. A process according to claim 2 wherein the condensation reaction is terminated when the cloud point is between 45°C and 50°C.
10. A process according to claim 2 wherein the condensation reaction is terminated by rapidly cooling the condensation reactants to a temperature in a range of from 30°C to 40 C.
11. A process according to claim 10 wherein the con-densation reaction is terminated by rapidly cooling the condensation reactants to a temperature in a range of from 33 C to 37 C.
12. A process according to claim 2 wherein the ether-ification reaction is initiated by the gradual addition of a concentrated acid to the condensation reactants until the pH
is lowered to between about 1.5 and 3.
is lowered to between about 1.5 and 3.
13. A process according to claim 2 wherein the acid-ification is conducted over a time interval ranging from between 25 to 35 minutes.
14. A process according to claim 13 wherein the acid-ification is conducted over a time interval ranging from between 28 to 32 minutes.
15. A process according to claim 13 wherein the pH of about 1.5 is utilized for etherification temperatures of about 25 C, a pH of about 3 is utilized for etherification tempera-tures of about 40 C, and pHs between about 1.8 and 2.2 are utilized for etherification temperatures in a range from about 33 C to about 37 C.
16. A process according to claim 15 wherein the duration of the etherification reaction, timed from the begin-ning of the introduction of the acid, is in a range of from about 50 to about 180 minutes.
17. A process according to claim 16 wherein the time duration of the etherification reaction is in a range of from 105 to 135 minutes.
18. A process according to claim 17 wherein the etherification reaction is terminated when a cloud point temp-erature of between about 45°C and 55°C is reached.
19. A process according to claim 2 wherein the ether-ification reaction is terminated by neutralizing the pH of the reactants through the addition of triethanolamine.
20. A process according to claim 2 wherein the ether-ification reaction is terminated by partially neutralizing the pH of the reactants by the addition of triethanolamine and completing the neutralization by the addition of sodium hydroxide.
21. A process according to claim 2 wherein the stabil-ization is achieved by maintaining the reactants at a tempera-ture in a range of from 50°C to 90°C for a period of time ranging from two to five hours.
22. A process according to claim 21 wherein the stabil-ization temperature is maintained between 70°C and 85°C.
23. A process according to claim 3 wherein the free formaldehyde of the stabilized solution is reduced to less than 6% by weight by the addition of urea and then left to cool naturally for 12 to 24 hours,
24. A process according to claim 2 wherein the melamine is added to the condensation reaction mixture in a period of time ranging from about ten to about fifteen minutes.
25. A process according to claim 2 wherein the polyols are ethylene glycol, diethylene glycol, triethylene glycol, glycerol, saccharose or d-glucose,
26. A process according to claim 25 wherein the polyol is ethylene glycol.
27. A process according to claim 26 wherein the polyol is a mixture of ethylene glycol and saccharose.
28. A process according to claim 2 wherein the aqueous condensation solution is acidified by the addition of sulfuric acid, hydrochloric acid, orthophosphoric acid, nitric acid, formic acid, or monochloracetic acid.
29. A process according to claim 2 wherein the aqueous condensation solution is acidified over a period of time between 25 and 35 minutes.
30. A process according to claim 29 wherein the aqueous condensation solution is acidified over a period of time of between 28 and 32 minutes.
31. A process according to claim 3 wherein urea in solid form is added in a quantity ranging from 0.6 to 1.6 mole per mole of melamine.
32. A process according to claim 31 wherein the urea is added in a quantity ranging between 0.8 and 1.2 mole per mole of melamine.
33. Aqueous solutions of etherified melamine-formalde-hyde resin prepared by the process of claim 2 and further characterized in that the dry extracts are between about 41%
and about 52% by weight, the F/M molar ratio is between 5 and 11, the P/M molar ratio is between 3 and 5, and the U/M ratio is between 0.6 and 1.6.
and about 52% by weight, the F/M molar ratio is between 5 and 11, the P/M molar ratio is between 3 and 5, and the U/M ratio is between 0.6 and 1.6.
34. Aqueous solutions according to claim 33 wherein the free formaldehyde content is less than 6%.
35. Aqueous solutions according to claim 34 wherein the solutions, when stored for a period of about two months at 25°C, have viscosities of less than about 800 centipoise and water compatibilities of at least about 1,200.
36. The process of claim 1 and further including the step of reducing the free formaldehyde content of the stabilized solution to less than 6%.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR7513569A FR2309575A1 (en) | 1975-04-30 | 1975-04-30 | AQUEOUS SOLUTIONS OF ETHERIFIED MELAMINE-FORMALDEHYDE RESINS WITH A LONG SHELF LIFE AND LOW FREE FORMALDEHYDE CONTENT |
| FR7513569 | 1975-04-30 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1091836A true CA1091836A (en) | 1980-12-16 |
Family
ID=9154670
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA251,045A Expired CA1091836A (en) | 1975-04-30 | 1976-04-26 | Aqueous solutions of etherified melamine-formaldehyde resins having long shelf life and low content of free formaldehyde |
Country Status (28)
| Country | Link |
|---|---|
| JP (1) | JPS5853648B2 (en) |
| AT (1) | AT344993B (en) |
| AU (1) | AU501880B2 (en) |
| BE (1) | BE841304A (en) |
| BR (1) | BR7602672A (en) |
| CA (1) | CA1091836A (en) |
| CH (1) | CH603737A5 (en) |
| CS (1) | CS191304B2 (en) |
| DD (1) | DD128380A5 (en) |
| DE (1) | DE2617232A1 (en) |
| ES (1) | ES447465A1 (en) |
| FI (1) | FI62547C (en) |
| FR (1) | FR2309575A1 (en) |
| GB (1) | GB1501534A (en) |
| HU (1) | HU177034B (en) |
| IE (1) | IE43271B1 (en) |
| IT (1) | IT1059948B (en) |
| LU (1) | LU74857A1 (en) |
| MX (1) | MX3319E (en) |
| NL (1) | NL190286C (en) |
| NO (1) | NO142444C (en) |
| NZ (1) | NZ180713A (en) |
| PL (1) | PL105541B1 (en) |
| RO (1) | RO70306A (en) |
| SE (1) | SE419229B (en) |
| TR (1) | TR19067A (en) |
| YU (1) | YU37352B (en) |
| ZA (1) | ZA762575B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110042701A (en) * | 2019-03-29 | 2019-07-23 | 广东福美新材料科技有限公司 | A kind of moisture retardant impregnated paper and preparation method thereof |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2715020C2 (en) * | 1977-04-04 | 1983-04-28 | Cassella Ag, 6000 Frankfurt | Process for the preparation of aqueous melamine / urea resin solutions |
| NZ206859A (en) * | 1983-02-07 | 1986-09-10 | Enigma Nv | Formaldehyde binder for boards prepared from lignocellulosic materials |
| GB2170208B (en) * | 1985-01-29 | 1988-06-22 | Enigma Nv | A formaldehyde binder |
| DE19633625A1 (en) * | 1996-08-21 | 1998-02-26 | Basf Ag | Process for the preparation of aqueous concentrated solutions of N-methylol ethers suitable for the finishing of cellulose-containing textile materials |
| RU2019134226A (en) * | 2019-10-25 | 2021-04-26 | Общество с ограниченной ответственностью "Комберри" | TRANSPARENT GEL-POLYMER ELECTROLYTES OF INCREASED CONDUCTIVITY BASED ON TRIAZINE COPOLYMERS |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1012319A (en) * | 1962-06-01 | 1965-12-08 | British Industrial Plastics | Water-soluble modified melamine-formaldehyde resins |
| DE2005166C3 (en) * | 1970-02-05 | 1975-05-15 | Chemische Fabrik Pfersee Gmbh, 8900 Augsburg | Process for the production of water-soluble, etherified methylolmelamines |
| GB1317774A (en) * | 1970-06-02 | 1973-05-23 | British Industrial Plastics | Melamine formaldehyde condensation products |
-
1975
- 1975-04-30 FR FR7513569A patent/FR2309575A1/en active Granted
-
1976
- 1976-04-06 GB GB13897/76A patent/GB1501534A/en not_active Expired
- 1976-04-12 IE IE777/76A patent/IE43271B1/en unknown
- 1976-04-20 DE DE19762617232 patent/DE2617232A1/en active Granted
- 1976-04-23 SE SE7604717A patent/SE419229B/en not_active IP Right Cessation
- 1976-04-26 CA CA251,045A patent/CA1091836A/en not_active Expired
- 1976-04-27 FI FI761168A patent/FI62547C/en not_active IP Right Cessation
- 1976-04-27 TR TR19067A patent/TR19067A/en unknown
- 1976-04-28 NZ NZ180713A patent/NZ180713A/en unknown
- 1976-04-28 RO RO7685931A patent/RO70306A/en unknown
- 1976-04-29 LU LU74857A patent/LU74857A1/xx unknown
- 1976-04-29 NL NLAANVRAGE7604581,A patent/NL190286C/en not_active IP Right Cessation
- 1976-04-29 CH CH540376A patent/CH603737A5/xx not_active IP Right Cessation
- 1976-04-29 BE BE166595A patent/BE841304A/en not_active IP Right Cessation
- 1976-04-29 ES ES447465A patent/ES447465A1/en not_active Expired
- 1976-04-29 BR BR2672/76A patent/BR7602672A/en unknown
- 1976-04-29 YU YU1084/76A patent/YU37352B/en unknown
- 1976-04-29 IT IT68046/76A patent/IT1059948B/en active
- 1976-04-29 DD DD7600192595A patent/DD128380A5/en unknown
- 1976-04-29 MX MX000201U patent/MX3319E/en unknown
- 1976-04-29 AU AU13464/76A patent/AU501880B2/en not_active Expired
- 1976-04-29 ZA ZA762575A patent/ZA762575B/en unknown
- 1976-04-29 HU HU76SA2917A patent/HU177034B/en unknown
- 1976-04-29 AT AT316676A patent/AT344993B/en not_active IP Right Cessation
- 1976-04-30 CS CS762877A patent/CS191304B2/en unknown
- 1976-04-30 JP JP51048690A patent/JPS5853648B2/en not_active Expired
- 1976-04-30 NO NO761499A patent/NO142444C/en unknown
- 1976-04-30 PL PL1976189203A patent/PL105541B1/en unknown
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110042701A (en) * | 2019-03-29 | 2019-07-23 | 广东福美新材料科技有限公司 | A kind of moisture retardant impregnated paper and preparation method thereof |
| CN110042701B (en) * | 2019-03-29 | 2023-09-15 | 广东福美新材料科技有限公司 | Moistureproof flame-retardant impregnated paper and preparation method thereof |
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