CA1175970A - Process for the preparation of a tack free urea/formaldehyde resin - Google Patents
Process for the preparation of a tack free urea/formaldehyde resinInfo
- Publication number
- CA1175970A CA1175970A CA000382882A CA382882A CA1175970A CA 1175970 A CA1175970 A CA 1175970A CA 000382882 A CA000382882 A CA 000382882A CA 382882 A CA382882 A CA 382882A CA 1175970 A CA1175970 A CA 1175970A
- Authority
- CA
- Canada
- Prior art keywords
- urea
- formaldehyde
- resin
- viscosity
- mole ratio
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
-
- 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
- C08G12/04—Condensation polymers of aldehydes or ketones with only compounds containing hydrogen attached to nitrogen of aldehydes with acyclic or carbocyclic compounds
- C08G12/10—Condensation polymers of aldehydes or ketones with only compounds containing hydrogen attached to nitrogen of aldehydes with acyclic or carbocyclic compounds with acyclic compounds having the moiety X=C(—N<)2 in which X is O, S or —N
- C08G12/12—Ureas; Thioureas
Landscapes
- Chemical & Material Sciences (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Phenolic Resins Or Amino Resins (AREA)
- Polyurethanes Or Polyureas (AREA)
- Treatments For Attaching Organic Compounds To Fibrous Goods (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A process for the preparation of a tack free urea/formaldehyde resin having a solids content of 64-66% and a viscosity at 25°C of 150-300 cps, in which a formaldehyde source is treated with a strong organic base, urea is added to obtain a formaldehyde/urea mole ratio lying between 1.90 and 2.35 : 1, the pH is adjusted to 5.0 - 6.3 with an acid, the polymerization reaction is stopped when the product has reached the required vicosity by an inorganic base and a further amount of urea is added such that the final formaldehyde/urea mole ratio becomes 1.38 to 1.70.
A process for the preparation of a tack free urea/formaldehyde resin having a solids content of 64-66% and a viscosity at 25°C of 150-300 cps, in which a formaldehyde source is treated with a strong organic base, urea is added to obtain a formaldehyde/urea mole ratio lying between 1.90 and 2.35 : 1, the pH is adjusted to 5.0 - 6.3 with an acid, the polymerization reaction is stopped when the product has reached the required vicosity by an inorganic base and a further amount of urea is added such that the final formaldehyde/urea mole ratio becomes 1.38 to 1.70.
Description
This invention relates to a process for the preparation of a tack free urea/fo~nalde~yde resin.
Urea/formaldehyde resins are particularly applicable in the manufacture of lignocellulosic material fibreboards.
The current practice is for the manufacture of such fibreboards to receive a urea/formaldehyde precondensate at his works and to prepare the resin fr~n such preconden~ate.
Urea/formaldehyde precondensates are commercially available high concentration formaldehyde solutions, stabilised with urea, appropriate for the manufacture of urea/formaldehyde resins.
The precondensate is reacted with urea ~or urea and melamine) to provid a resin which is used to impregnate the lignocellulosic fibres (preferably soft wo~ds are used, such as pine, eucalyptus, poplar, etc., but other woods and products such as bagasse, straw, etc. may be used) and the impregnated fibre is transferred thereafter to a press where the fibreboard is produced with heat and pressure. m is, nevertheless, is affected by various disadvantages.
In the first place, there is a high level of unstability, since the stability of the resin prepared in this way is less than 48 hours.
In the second place, the fibre is not correctly impregnated, since the instability of the resin means ~lat its degree of polyme~ization increases with time, making it impossible to obtain correct, stable fibre Lmpregnation ~
7~7~
conditions. This incorrect impregnation gives rise to the appearance of resin stains on the fibrebcard surface, with the disadvantage (apart frc~
the irregulax visual appearance of the board surface) cf causing problams at the time of applying finishes such as paint, va~nish, plastified papers, etc. by the different degree of absorption in the areas shcwing dry resin stains relative to the unstained areas.
In the third place, there are problems in the transfer of the impregnated fibre, since the incorrect fibre impregnation and the high degree of tack of the resin used, causes the ormation of lumps of bonded fibre (balls of borlded fibre), giving rise to serious problems in the transfer syste~s (air or mechanical) of the inpregnated fibre to the press.
It is also impossible to impregnate before the fibre has dried, since the resin being a quic~ curing one, only dry fibre may be impregnated (t~.at is, after passing through the dryer), since the passage of the impregna~ec fibre through a dryer causes pregelling before the m~terlal reaches the press, producing a fibreboard having poor mechanical properties.
, .
To solve the above problems, the invention provides a process of the aforementioned type, characterised fundamentally in that it comprises the steps of: treating a formaldehyde source with a strong organic base to ad}ust its pH to between 7.0 and 8.~; adding urea until the formaldehyde/
urea mole ratio is from 1.90 to 2.35; heating to boiling point; adjusting the pH to 5.0 6.3 with an acid, preferably fonmic acid; stopping the poly~erizatiorl reaction when the product has reached the desired viscosit~
with an inorganic base; adding a further amKunt of urea to the product as , .
.
-~ - 3 -3L~7 :~ , - it is cooling such that the for~aldehyde/urea mole ratio is fro~ 1.38 to 1.70 and adjusting the pH to 8.0-8.5 therèby providing a resin having a ",,,:,. ;
solids content of 64-66~ and a viscosity at ~ of 150-300 cps.
Accord mg to the inventic~, the strong organic kase is preferably chosen from among the group f~xmed by triisc,propanolamine, triethylamine and diethylamine.
'~' The invention further contemplates the addition of inorganic salts chosen from among the group formed by alkali metal halides, alkali earth meta}~
halides and alkali metal sulphates during the preparaticn to imprc~e the stability properties.
.`: .
It is also possible to replace part of the urea (1-15%) with corresponding stoichicmetric amounts of a product having a similar chemical behaviour, preferably melamune and dicyandiamide.
~; T~e follcwing resin properties are obtained with the resin produce~
by the process according to the invention:
. . .
- low viscosity, within the above mentioned range;
- tack free;
:, .
-stable at room te~perature for more than two months.
Optionally, the resin is used for naking impregnation preparations with different amounts of accelerators and retarders, allowing mLxtures with different gelling tL~es to be c~tained and, therewith, the possibilit~
of impregnating the fibre before or after drying, as desired.
~,, ;~' ^'~ .
, . . .. .
,- ~
~s~
The lignocellulosic material fibers, impregnated with an appropriatel~
catalysed ure~/formaldehyde resin, are transferred by aix or mechanical syst~ms to a hot platen press (hea.ed by steam, thermal oils or high frequency electric current) where tney are subjected to pressure and heat to produce a fibreboard.
The properties of the urea/fQrmaldehyde resin should be appropriate for obtaining correct impregnation of t~he fibre with a minimum resin comsum-=ion, giving correct mechanical properties of the fibreboardO The behaviour o~ t~e fibre, whlch is the product to be impregnated, relative to resin absorp.ion is different from the hereto kn ~ one of wocd shaving or particles (production of fibrebcard with ure_'formaldehyde resins or glues) and t~
of plywood (production of plywocd also with urea/formaldehyde resins or lues~
.~
The combination of properties required in the resin to be able to impregnate the ~ibre correctly is o~tained by the correction conjugatio-.
of certain factors during the resin production, such factors being essentially: formol-urea mole ratios in the initial and f m al stages o~
the resin; p~ and t~mperature in the reaction; final resin viscosity.
.,~ .
Likewise, to improve certain properties (resin stability time, mec~.anicz ; properties of the finished fibreboard), there may be used in the manufa^~.ure ; of the resin inorganic salts such as: alkali metal or alkali earth meta' halides or alkali metal sulphates in amounts which may va~y between:
weight inorganic salt 0.17 > - ~ 0.02 weigt dr~ resin ,''' ; ': ~, . - '',~ ' ~ - 5 -759~
The catalysed resin gelling t~me should be appropriate to: ~
avoid pregelling during the transfer (or transfer and drying in certain cases) to the press;
keep the press time as short as possible, so that the n~unum economic yield may be obtained from the press while maintain mg the appropriate quality in the bonded fibreboard thus obtained.
." ~.
The res m is catalysed before the impregnation step, using normally strong acid ammonium salts,although other weak acid products may also be used.
The fibre may be impregnated ~ith the resin in the dry or in the wet state. In both cases, metering means is required to regulate the proportions of fibre and resin. The normal weig:rlt ratio used is as follcws:
weight dry resin ---- = 0.07 - 0.11 weight dry fibre ; Any of the commercially available products, such as different formal-dehyde concentration aqueaus solutions or urea-formaldehyde or paraformal-dehyde precondensates, may be used as formaldehyde source in the preparation of the resins of the invention.
The abcve precondensates generally have the follcwing properties:
Active urea~formaldehyde concentration: 60 to 85 ~ Formaldehyde/urea mcle ratio 4:1 to 6:1 .' .
~' '". :
.
: ................................... ' . ~ ', :~
:
-.
~597~
I~hese precondensates afford the advantage of containing a high con-centration of formaldehyde, ~t the same time as they are very stable (in excess of 6 months) and their manufacture ~reatly simplifies the production of urea/fornaldehyde resins.
' E~IE 1 To 100 kg of a urea/formaldehyde precondensate having a formaldehyde~
urea mole ratio of 5 and an active urea~formaldehyde concentration of 70 (50% formaldehyde and 20% urea) at pH 7~5, there was added cold 32 kg o~
urea such that the formaldehyde/urea mole ratio became 1.92 : 1 and the mixture was heated to boiling point.
'`;
The mixture was refluxed for 3; minutes and the pH was adjusted to 8.0 with triisopropanolal~ine. Like effects would be obtained with other bases such as triethylamune and diethylamlne.
.~ .
Thereafter the pH was adjust~d to 6.0 with formic acid, the pH and the viscosity being checked periodically.
.~ .
The polymerisation reaction WQS stopped by addition of sodium hydrGxide when the viscosity of the mixture at ~ was 400 cps.
The muxture was then coo}ed to 65~C and a further 20 kg of urea were added to adjust the formaldehyde/urea mole ratio to 1.39 : 1. After this addition, the product was oooled to 20QC and the pH was finally adjusted to 8.0 with sodium hydroxide.
~ , .
~ The thus obtained resin ~152 kg) had a solids content of 65% and a ~ 7 ~7S~
viscosity at 25QC of 225 cps.
.
The pH of a 120 kg S0 weight % formaldehyde aqueous solution was adjusl to 8.0 with triisopropanolam me, and there was added thereto with heating 57 kg of urea such that the formaldehyde/urea mole ratio became 2,10 : 1 and the mixture was heated to boiling point~ The mixtuxe was refluxed for 20 mlnutes and thereafter the pH was adjusted to 5.5 with formlc acid, the pH and the viscosity being checked periodically.
The polymerization reaction was stopped by addition of sodium hydroxid~
when the viscosity~of the mix at ~e was 70 cps.
;:
~5~
The ~ixtlre was then cooled to1~5~e and a further 20 kg of urea was added to adjust the formaldehyde/urea mole ratio to 1.53 : 1. The product was cooled after this addition.
.
`~ m e excess water was removed by distillation under vacuum and the resi~
was cooled to ~ . The pH was adjusted to 8Ø
The thus obtained resin (175 kg) has a so].ids content of 65~ and a c25G
viscosity ati~5~e-of 225 cps.
. ~
The pH of a 150 kg 36.6 weight % aqueous formaldehyde solution was adjusted to 8.0 using triisopropanolamine. There were added cold 47 kg of urea such that the formaldehyde/urea mole ratio became 2.34 : 1 and the mixture was heated to boiling point. The mixture was refluxed for 35 minute and thereafter the pH was adjusted to 5.0 with formic acid, the pH and the , ~ :
, .
. . ; , viscosity being checked periodicalk~.
, . .
The polymerization reaction was stopped by addition of sodium hydroxide when the viscosity of the ~uxture at ~ was 20 cps.
~j~o~, The rnixture was th~n cooled to G.~e c~nd a further 18 kg of urea were added such that the formaldehyde/urea mole ratio became 1.70 : 1. The product was cooled after this addition.
The excess water was rem~ved by distillation under vacuum and the resin ~; :
was cooled to i~@e. The p~ was adjusted to 8Ø
. . .
The thus cbtain2d resin (151 kg approx) had a solids content of 65 and a viscosity at ~ of 225 cps.
:; .
Ex~MæLE 4 100 kg of a urea/formaldehyde precondensate having a formaldehyde/urea mole ratio of 5 and an active urea~formaldehyde concentration of 80% (57%
formaldehyde and 23% urea) were heat~d to-65~. The pH was adjusted to 8.Q
by addition of triethylamine.
., :
Thereafter 6 kg of potassium ~ oride was dissolved in the precondensate wlth the required amount of water (18 kg) to hold the final solids content a the resin to its normal value of 65% and the ~mount of inorganic salt added was such that the inorganic salt/formaldehyde mole ratio was 0.042 : 1.
When the potassium chloride was completely dissolved (ter~perature 60~C) 26 kg of urea were added such that the formaldehyde/urea mole ratio became ~ 2.34 : 1 and the mixture was heated to boiling point.
`~:
:........... . .
., , ~
The mixture was refluxed and the pH and viscosity were checked periodically. The pH was held to 6.0 with formlc acid.
m e polymerization reaction was stopped by addition of so~ium hydroxide when the viscosity of the muxture was 400 cps.
The mlxture was then cooled to 65~C and a further 18 kg of urea were . added such that the formaldehyde/urea mole ratio was adjusted to 1.70 : 1.
After this addition, the product was cooled to ~ and the pH was finally adjusted to 8Ø
,:
: The thus obtained resin (168 kg) had a solids oontent of 65% and a . G~SC~
viscosity at ~e of 225cps.
''' ' ;,, .
. . .
' ;' . .
~, . . .
Urea/formaldehyde resins are particularly applicable in the manufacture of lignocellulosic material fibreboards.
The current practice is for the manufacture of such fibreboards to receive a urea/formaldehyde precondensate at his works and to prepare the resin fr~n such preconden~ate.
Urea/formaldehyde precondensates are commercially available high concentration formaldehyde solutions, stabilised with urea, appropriate for the manufacture of urea/formaldehyde resins.
The precondensate is reacted with urea ~or urea and melamine) to provid a resin which is used to impregnate the lignocellulosic fibres (preferably soft wo~ds are used, such as pine, eucalyptus, poplar, etc., but other woods and products such as bagasse, straw, etc. may be used) and the impregnated fibre is transferred thereafter to a press where the fibreboard is produced with heat and pressure. m is, nevertheless, is affected by various disadvantages.
In the first place, there is a high level of unstability, since the stability of the resin prepared in this way is less than 48 hours.
In the second place, the fibre is not correctly impregnated, since the instability of the resin means ~lat its degree of polyme~ization increases with time, making it impossible to obtain correct, stable fibre Lmpregnation ~
7~7~
conditions. This incorrect impregnation gives rise to the appearance of resin stains on the fibrebcard surface, with the disadvantage (apart frc~
the irregulax visual appearance of the board surface) cf causing problams at the time of applying finishes such as paint, va~nish, plastified papers, etc. by the different degree of absorption in the areas shcwing dry resin stains relative to the unstained areas.
In the third place, there are problems in the transfer of the impregnated fibre, since the incorrect fibre impregnation and the high degree of tack of the resin used, causes the ormation of lumps of bonded fibre (balls of borlded fibre), giving rise to serious problems in the transfer syste~s (air or mechanical) of the inpregnated fibre to the press.
It is also impossible to impregnate before the fibre has dried, since the resin being a quic~ curing one, only dry fibre may be impregnated (t~.at is, after passing through the dryer), since the passage of the impregna~ec fibre through a dryer causes pregelling before the m~terlal reaches the press, producing a fibreboard having poor mechanical properties.
, .
To solve the above problems, the invention provides a process of the aforementioned type, characterised fundamentally in that it comprises the steps of: treating a formaldehyde source with a strong organic base to ad}ust its pH to between 7.0 and 8.~; adding urea until the formaldehyde/
urea mole ratio is from 1.90 to 2.35; heating to boiling point; adjusting the pH to 5.0 6.3 with an acid, preferably fonmic acid; stopping the poly~erizatiorl reaction when the product has reached the desired viscosit~
with an inorganic base; adding a further amKunt of urea to the product as , .
.
-~ - 3 -3L~7 :~ , - it is cooling such that the for~aldehyde/urea mole ratio is fro~ 1.38 to 1.70 and adjusting the pH to 8.0-8.5 therèby providing a resin having a ",,,:,. ;
solids content of 64-66~ and a viscosity at ~ of 150-300 cps.
Accord mg to the inventic~, the strong organic kase is preferably chosen from among the group f~xmed by triisc,propanolamine, triethylamine and diethylamine.
'~' The invention further contemplates the addition of inorganic salts chosen from among the group formed by alkali metal halides, alkali earth meta}~
halides and alkali metal sulphates during the preparaticn to imprc~e the stability properties.
.`: .
It is also possible to replace part of the urea (1-15%) with corresponding stoichicmetric amounts of a product having a similar chemical behaviour, preferably melamune and dicyandiamide.
~; T~e follcwing resin properties are obtained with the resin produce~
by the process according to the invention:
. . .
- low viscosity, within the above mentioned range;
- tack free;
:, .
-stable at room te~perature for more than two months.
Optionally, the resin is used for naking impregnation preparations with different amounts of accelerators and retarders, allowing mLxtures with different gelling tL~es to be c~tained and, therewith, the possibilit~
of impregnating the fibre before or after drying, as desired.
~,, ;~' ^'~ .
, . . .. .
,- ~
~s~
The lignocellulosic material fibers, impregnated with an appropriatel~
catalysed ure~/formaldehyde resin, are transferred by aix or mechanical syst~ms to a hot platen press (hea.ed by steam, thermal oils or high frequency electric current) where tney are subjected to pressure and heat to produce a fibreboard.
The properties of the urea/fQrmaldehyde resin should be appropriate for obtaining correct impregnation of t~he fibre with a minimum resin comsum-=ion, giving correct mechanical properties of the fibreboardO The behaviour o~ t~e fibre, whlch is the product to be impregnated, relative to resin absorp.ion is different from the hereto kn ~ one of wocd shaving or particles (production of fibrebcard with ure_'formaldehyde resins or glues) and t~
of plywood (production of plywocd also with urea/formaldehyde resins or lues~
.~
The combination of properties required in the resin to be able to impregnate the ~ibre correctly is o~tained by the correction conjugatio-.
of certain factors during the resin production, such factors being essentially: formol-urea mole ratios in the initial and f m al stages o~
the resin; p~ and t~mperature in the reaction; final resin viscosity.
.,~ .
Likewise, to improve certain properties (resin stability time, mec~.anicz ; properties of the finished fibreboard), there may be used in the manufa^~.ure ; of the resin inorganic salts such as: alkali metal or alkali earth meta' halides or alkali metal sulphates in amounts which may va~y between:
weight inorganic salt 0.17 > - ~ 0.02 weigt dr~ resin ,''' ; ': ~, . - '',~ ' ~ - 5 -759~
The catalysed resin gelling t~me should be appropriate to: ~
avoid pregelling during the transfer (or transfer and drying in certain cases) to the press;
keep the press time as short as possible, so that the n~unum economic yield may be obtained from the press while maintain mg the appropriate quality in the bonded fibreboard thus obtained.
." ~.
The res m is catalysed before the impregnation step, using normally strong acid ammonium salts,although other weak acid products may also be used.
The fibre may be impregnated ~ith the resin in the dry or in the wet state. In both cases, metering means is required to regulate the proportions of fibre and resin. The normal weig:rlt ratio used is as follcws:
weight dry resin ---- = 0.07 - 0.11 weight dry fibre ; Any of the commercially available products, such as different formal-dehyde concentration aqueaus solutions or urea-formaldehyde or paraformal-dehyde precondensates, may be used as formaldehyde source in the preparation of the resins of the invention.
The abcve precondensates generally have the follcwing properties:
Active urea~formaldehyde concentration: 60 to 85 ~ Formaldehyde/urea mcle ratio 4:1 to 6:1 .' .
~' '". :
.
: ................................... ' . ~ ', :~
:
-.
~597~
I~hese precondensates afford the advantage of containing a high con-centration of formaldehyde, ~t the same time as they are very stable (in excess of 6 months) and their manufacture ~reatly simplifies the production of urea/fornaldehyde resins.
' E~IE 1 To 100 kg of a urea/formaldehyde precondensate having a formaldehyde~
urea mole ratio of 5 and an active urea~formaldehyde concentration of 70 (50% formaldehyde and 20% urea) at pH 7~5, there was added cold 32 kg o~
urea such that the formaldehyde/urea mole ratio became 1.92 : 1 and the mixture was heated to boiling point.
'`;
The mixture was refluxed for 3; minutes and the pH was adjusted to 8.0 with triisopropanolal~ine. Like effects would be obtained with other bases such as triethylamune and diethylamlne.
.~ .
Thereafter the pH was adjust~d to 6.0 with formic acid, the pH and the viscosity being checked periodically.
.~ .
The polymerisation reaction WQS stopped by addition of sodium hydrGxide when the viscosity of the mixture at ~ was 400 cps.
The muxture was then coo}ed to 65~C and a further 20 kg of urea were added to adjust the formaldehyde/urea mole ratio to 1.39 : 1. After this addition, the product was oooled to 20QC and the pH was finally adjusted to 8.0 with sodium hydroxide.
~ , .
~ The thus obtained resin ~152 kg) had a solids content of 65% and a ~ 7 ~7S~
viscosity at 25QC of 225 cps.
.
The pH of a 120 kg S0 weight % formaldehyde aqueous solution was adjusl to 8.0 with triisopropanolam me, and there was added thereto with heating 57 kg of urea such that the formaldehyde/urea mole ratio became 2,10 : 1 and the mixture was heated to boiling point~ The mixtuxe was refluxed for 20 mlnutes and thereafter the pH was adjusted to 5.5 with formlc acid, the pH and the viscosity being checked periodically.
The polymerization reaction was stopped by addition of sodium hydroxid~
when the viscosity~of the mix at ~e was 70 cps.
;:
~5~
The ~ixtlre was then cooled to1~5~e and a further 20 kg of urea was added to adjust the formaldehyde/urea mole ratio to 1.53 : 1. The product was cooled after this addition.
.
`~ m e excess water was removed by distillation under vacuum and the resi~
was cooled to ~ . The pH was adjusted to 8Ø
The thus obtained resin (175 kg) has a so].ids content of 65~ and a c25G
viscosity ati~5~e-of 225 cps.
. ~
The pH of a 150 kg 36.6 weight % aqueous formaldehyde solution was adjusted to 8.0 using triisopropanolamine. There were added cold 47 kg of urea such that the formaldehyde/urea mole ratio became 2.34 : 1 and the mixture was heated to boiling point. The mixture was refluxed for 35 minute and thereafter the pH was adjusted to 5.0 with formic acid, the pH and the , ~ :
, .
. . ; , viscosity being checked periodicalk~.
, . .
The polymerization reaction was stopped by addition of sodium hydroxide when the viscosity of the ~uxture at ~ was 20 cps.
~j~o~, The rnixture was th~n cooled to G.~e c~nd a further 18 kg of urea were added such that the formaldehyde/urea mole ratio became 1.70 : 1. The product was cooled after this addition.
The excess water was rem~ved by distillation under vacuum and the resin ~; :
was cooled to i~@e. The p~ was adjusted to 8Ø
. . .
The thus cbtain2d resin (151 kg approx) had a solids content of 65 and a viscosity at ~ of 225 cps.
:; .
Ex~MæLE 4 100 kg of a urea/formaldehyde precondensate having a formaldehyde/urea mole ratio of 5 and an active urea~formaldehyde concentration of 80% (57%
formaldehyde and 23% urea) were heat~d to-65~. The pH was adjusted to 8.Q
by addition of triethylamine.
., :
Thereafter 6 kg of potassium ~ oride was dissolved in the precondensate wlth the required amount of water (18 kg) to hold the final solids content a the resin to its normal value of 65% and the ~mount of inorganic salt added was such that the inorganic salt/formaldehyde mole ratio was 0.042 : 1.
When the potassium chloride was completely dissolved (ter~perature 60~C) 26 kg of urea were added such that the formaldehyde/urea mole ratio became ~ 2.34 : 1 and the mixture was heated to boiling point.
`~:
:........... . .
., , ~
The mixture was refluxed and the pH and viscosity were checked periodically. The pH was held to 6.0 with formlc acid.
m e polymerization reaction was stopped by addition of so~ium hydroxide when the viscosity of the muxture was 400 cps.
The mlxture was then cooled to 65~C and a further 18 kg of urea were . added such that the formaldehyde/urea mole ratio was adjusted to 1.70 : 1.
After this addition, the product was cooled to ~ and the pH was finally adjusted to 8Ø
,:
: The thus obtained resin (168 kg) had a solids oontent of 65% and a . G~SC~
viscosity at ~e of 225cps.
''' ' ;,, .
. . .
' ;' . .
~, . . .
Claims (9)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for the preparation of a tack free urea/formaldehyde resin comprising the steps of:
treating a formaldehyde source with a strong organic base to adjust the pH thereof to between 7.0 and 8.0; adding urea until the formaldehyde/urea mole ratio is from 1.90 to 2.35:1; heating to boiling point; adjusting the pH to 5.0 - 6.3 with an acid; stopping the polymerization reaction when the product has reached the desired viscosity with an inorganic base; adding a further amount of urea to the product as it is cooling such that the final formaldehyde/urea mole ratio is from 1.38 to 1.70 and adjusting the pH to 8.0 - 8.5, thereby providing a resin having a solids content of 64 - 66% and a viscosity at 25°C of 150 - 130 cps.
treating a formaldehyde source with a strong organic base to adjust the pH thereof to between 7.0 and 8.0; adding urea until the formaldehyde/urea mole ratio is from 1.90 to 2.35:1; heating to boiling point; adjusting the pH to 5.0 - 6.3 with an acid; stopping the polymerization reaction when the product has reached the desired viscosity with an inorganic base; adding a further amount of urea to the product as it is cooling such that the final formaldehyde/urea mole ratio is from 1.38 to 1.70 and adjusting the pH to 8.0 - 8.5, thereby providing a resin having a solids content of 64 - 66% and a viscosity at 25°C of 150 - 130 cps.
2. A process as claimed in claim 1 in which the acid is formic acid.
3. The process of claim 1, wherein the strong organic base is chosen from among the group formed by triisopropanolamine, triethylamine and diethylamine.
4. The process of claim 1, wherein the resin stability properties are improved by the addition during preparation of inorganic salts chosen from among the group formed by alkali metal halides, alkali earth metal halides and alkali sulphates.
5. The process of claim l, wherein from l to 15% of the urea is replaced by a product having a similar chemical behaviour.
6. The process as claimed in claim 5 wherein said product is melamine or dicyandiamide.
7. The process of claim 1, wherein the formaldehyde source is a urea/formaldehyde precondensate, the first urea addition is in cold, followed by heating, the pH is adjusted to 7.0 - 7.5 by said strong organic base treatment and the polymerization reaction is stopped when the viscosity is 350 - 450 cps.
8. The process of claim l, wherein the formaldehyde source is a 50 weight % aqueous formaldehyde solution, the pH is adjusted to 8.0 - 8.3 by said strong organic base treatment, the first urea addition is hot such that the formaldehyde/urea mole ratio becomes close to 2.10:1 and the polymerization reaction is stopped when the viscosity is 40-100 cps.
9. The process of claim l, wherein the formaldehyde source is a 36.6 weight % aqueous formaldehyde solution, the pH is adjusted to 8.0 - 8.3 by said strong organic base treatment, the first urea addition is cold such that the formaldehyde/urea mole ratio becomes close to 2.34:1 and the polymerization reaction is stopped when the viscosity is 15 - 25 cps.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| ES494322A ES8106163A1 (en) | 1980-08-18 | 1980-08-18 | Process for the preparation of a non-tacky urea-formaldehyde resin |
| ES494,322 | 1980-08-18 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1175970A true CA1175970A (en) | 1984-10-09 |
Family
ID=8480971
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000382882A Expired CA1175970A (en) | 1980-08-18 | 1981-07-30 | Process for the preparation of a tack free urea/formaldehyde resin |
Country Status (8)
| Country | Link |
|---|---|
| AR (1) | AR226474A1 (en) |
| AT (1) | AT387226B (en) |
| CA (1) | CA1175970A (en) |
| DE (1) | DE3132280A1 (en) |
| ES (1) | ES8106163A1 (en) |
| MX (1) | MX158011A (en) |
| NO (1) | NO156980C (en) |
| SE (1) | SE450385B (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DD283732A7 (en) * | 1988-10-21 | 1990-10-24 | ������@�����`������@ ���@������� k�� | METHOD FOR PRODUCING A REACTIVE UREA FORMALDEHYDE RESIN LIME |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| IT951962B (en) * | 1971-12-27 | 1973-07-10 | Sir Soc Italiana Resine Spa | PROCEDURE FOR THE PREPARATION OF RESINS FROM UREA AND FORMALDEHYDE |
| US3994850A (en) * | 1976-01-05 | 1976-11-30 | Champion International Corporation | Modified urea-formaldehyde resin adhesive |
| OA06231A (en) * | 1978-04-07 | 1981-06-30 | Patentes Novedades Sa | Process for preparing urea-formaldehyde glues containing an inorganic salt. |
| DE2825590C2 (en) * | 1978-06-10 | 1983-05-05 | Th. Goldschmidt Ag, 4300 Essen | Process for the production of thermosetting urea-formaldehyde resins and their use |
-
1980
- 1980-08-18 ES ES494322A patent/ES8106163A1/en not_active Expired
-
1981
- 1981-06-04 MX MX187640A patent/MX158011A/en unknown
- 1981-07-27 AT AT0330081A patent/AT387226B/en not_active IP Right Cessation
- 1981-07-30 CA CA000382882A patent/CA1175970A/en not_active Expired
- 1981-08-06 AR AR286357A patent/AR226474A1/en active
- 1981-08-07 SE SE8104754A patent/SE450385B/en not_active IP Right Cessation
- 1981-08-14 DE DE19813132280 patent/DE3132280A1/en not_active Withdrawn
- 1981-08-14 NO NO812759A patent/NO156980C/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| SE8104754L (en) | 1982-02-19 |
| NO156980C (en) | 1987-12-30 |
| AT387226B (en) | 1988-12-27 |
| ATA330081A (en) | 1988-05-15 |
| DE3132280A1 (en) | 1982-06-16 |
| MX158011A (en) | 1988-12-29 |
| NO812759L (en) | 1982-02-19 |
| ES494322A0 (en) | 1981-08-01 |
| AR226474A1 (en) | 1982-07-15 |
| SE450385B (en) | 1987-06-22 |
| NO156980B (en) | 1987-09-21 |
| ES8106163A1 (en) | 1981-08-01 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |