EP3612586A1 - Phenol-free impregnation resin - Google Patents
Phenol-free impregnation resinInfo
- Publication number
- EP3612586A1 EP3612586A1 EP18728202.5A EP18728202A EP3612586A1 EP 3612586 A1 EP3612586 A1 EP 3612586A1 EP 18728202 A EP18728202 A EP 18728202A EP 3612586 A1 EP3612586 A1 EP 3612586A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- lignin
- formaldehyde
- resin
- process according
- weight
- 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.)
- Withdrawn
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08H—DERIVATIVES OF NATURAL MACROMOLECULAR COMPOUNDS
- C08H6/00—Macromolecular compounds derived from lignin, e.g. tannins, humic acids
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07G—COMPOUNDS OF UNKNOWN CONSTITUTION
- C07G1/00—Lignin; Lignin derivatives
-
- 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
- C08G8/00—Condensation polymers of aldehydes or ketones with phenols only
- C08G8/04—Condensation polymers of aldehydes or ketones with phenols only of aldehydes
- C08G8/08—Condensation polymers of aldehydes or ketones with phenols only of aldehydes of formaldehyde, e.g. of formaldehyde formed in situ
- C08G8/20—Condensation polymers of aldehydes or ketones with phenols only of aldehydes of formaldehyde, e.g. of formaldehyde formed in situ with polyhydric phenols
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
- C09J161/00—Adhesives based on condensation polymers of aldehydes or ketones; Adhesives based on derivatives of such polymers
- C09J161/04—Condensation polymers of aldehydes or ketones with phenols only
- C09J161/06—Condensation polymers of aldehydes or ketones with phenols only of aldehydes with phenols
- C09J161/12—Condensation polymers of aldehydes or ketones with phenols only of aldehydes with phenols with polyhydric phenols
Definitions
- the present invention relates to a process for the production of essentially phenol-free impregnation resin, the resin produced by this process or otherwise having a similar composition, as well as end-uses of the resin.
- the resins commonly used in impregnation are either phenol resins or melamine resins, in each case depending on the application of the impregnated paper. While phenol resins are a viable option in a number of applications, melamine resins are used when aiming at improved water resistance and similar properties. Certain applications require the properties of both resins, in which case a mixture of melamine and phenol resins is being used. Melamine resins are more expensive than phenol resins in their raw materials, but they are more safe, because they do not contain free phenol, which is toxic.
- the structure and properties of finished resin are dependent on the reaction conditions employed in production, such as e.g. condensation temperature, condensation time, catalyst system, solvent system and the formaldehyde/phenol molar ratio.
- the choice of reaction conditions depends on the end-use for which the resin is being made.
- the present invention comprises a process for the production of essentially phenol-free impregnation resin by using essentially only lignin as the material comprising phenolic OH groups, and a resin produced by this process or otherwise having a similar composition.
- formaldehyde is condensed with lignin in the presence of a catalyst at an elevated temperature.
- the invention is based on the idea that lignin is first brought into the liquid phase by dissolving it into a solvent or solvent mixture, after which formaldehyde is added into the solution thus obtained in the presence of an alkaline catalyst to bring about a condensation reaction between formaldehyde and lignin. Alkali is being fed gradually into the liquid stage, whereby the reaction of formaldehyde with the phenolic groups can be taken into completion.
- an essentially phenol-free impregnation resin is accomplished, which resin comprises a condensation product of formaldehyde and lignin, wherein the concentration of free formaldehyde is not more than 5 wt.-%, especially not more than 1 wt.-%, for example 0.1 to 1.0 wt.-%.
- the finished impregnation resin is most preferably in the form of an aqueous mixture in which the dry matter content with respect to the resin is higher than about 20 wt.-% and usually not more than about 70 wt.-%, typically the dry matter content of the resin is between 30 and 40 wt.-%.
- phenol in the phenol-formaldehyde impregnation resin is essentially completely replaced with lignin, alternatively allowing a complete avoidance of the use of the toxic phenol.
- the invention allows the control and adjustment of the reactivity of the condensation reaction between lignin and formaldehyde. In the process, the resin can be condensed so that virtually all free formaldehyde is brought into reaction. Low levels of free
- formaldehyde can be achieved by the cooking system according to the invention, whereby the solution can be used in many applications in which low formaldehyde levels are required. At the same time, it is possible to render the viscosity of the resin to a level allowing its use in paper impregnation applications. Such impregnated fiber sheets can be used for the production of composite veneer products, for example.
- the resin produced by the process of the invention or a resin having a corresponding composition is thus suitable for general use as a substitute for conventional impregnation resin e.g. in film and core papers.
- impregnation resins possible applications include various fiberboards, for example.
- Figure 2 is a schematic exploded view of the structure of the compact laminate.
- Resin refers to a reaction product obtained via a polymerization reaction of a starting material comprising phenolic OH groups, and formaldehyde.
- the phenol-free resin is produced by using essentially only lignin as the material comprising phenolic OH groups.
- at least 90 weight-%, preferably at least 95 weight-%, most preferably at least 98 weight-%, or even 100 weight-% of the raw material comprising phenolic OH groups is lignin.
- another biomass such as tannin, is used as the material comprising phenolic OH groups in addition to lignin.
- Lignin used in the present invention is especially lignin obtained from a biomass, such as wood or annual or perennial plants or, correspondingly, lignin obtained from
- lignocellulose In particular, material isolated from spent liquor obtained from cooking of biomass is used as the lignin starting material.
- lignin starting material As examples of lignin starting material to be used, mention may be made of lignin isolated from biomass by an alkaline cooking process, such as kraft lignin (i.e. lignin from sulphate process) or soda lignin (i.e. lignin from soda pulping). The use of organosolv lignin (i.e. lignin obtained from organosolv pulping) is also possible in the process. As lignin starting materials that can be used, mention can also be made of pyrolytic lignin, steamed lignin, diluted acid lignin and alkaline oxidative lignin. Mixtures of the above-mentioned lignin starting materials may also be used as the lignin starting material.
- the lignin starting material may also contain other materials, such as extracts or carbohydrates, such as cellulose or hemicellulose or degradation products thereof.
- the lignin starting material comprises at least 90 weight- , most suitably at least 95 weight-%, especially at least 98 weight-% lignin.
- the lignin starting material may be in the form of a solid, such as powder. This type of lignin starting materials is represented by commercially marketed lignin products. It is also possible to use liquid stage lignin, as will be described in more detail below.
- Production takes place by dissolving the lignin starting material into a solvent comprising an alkaline substance as catalyst.
- Formaldehyde especially an aqueous solution of formaldehyde, i.e. formalin, is added to the solution.
- the lignin and formaldehyde are subsequently condensed at an elevated temperature until virtually all formaldehyde, i.e. at least 90 weight-%, more preferably at least 95 weight-%, most suitably at least 99 weight- % of the formaldehyde has reacted.
- the resin thus formed in collected.
- the lignin and formaldehyde are condensed at a temperature of about 50 to 90 °C until all formaldehyde has reacted, whereafter the resin is collected.
- lignin and formaldehyde are most preferably condensed in the liquid stage formed by the lignin solvent or a mixture thereof.
- lignin is in the production process of the resin dissolved at the beginning of resin cooking into a solvent mixture comprising the solvent, water and the alkaline catalyst. The addition of solvent and water at the beginning of resin cooking makes controlling of viscosity possible during condensation so that viscosity does not rise too high at any reaction stage.
- the catalyst can also de dosed in a number of portions, which also facilitates the control of steady proceeding of the condensation reactions. Owing to dosing of the solvent, water and the catalyst as well as the ways of dosing them, it will be possible to condense the resin to a point where free formaldehyde has reacted virtually completely.
- kraft lignin is used to replace phenol.
- This type of lignin also available commercially, is usually supplied as a powder, whereby the dry matter content of lignin is over 90 weight-%, e.g. about 93 weight-%.
- the process also allows the use of an aqueous slurry of lignin having a dry matter content of about 50 weight-% or higher.
- the dry matter content can thus be at least 60 weight-%, for example at least 70 weight-%. In one embodiment the dry matter content is about 75 weight-%.
- the solvent for lignin is typically a polar liquid which is miscible with water.
- the solvent mention may be made of aliphatic and aromatic alcohols such as methanol, and aliphatic ketones such as acetone.
- the solvent is used in an amount sufficient to maintain a suitable dry matter content in the mixture, i.e. between about 20 to 70 weight-%, in particular 30 to 70 weight-%, considering the further reaction.
- the lignin is dissolved into a mixture of the actual solvent and water.
- Methanol or mixtures thereof, such as aqueous solution of methanol, are usually used as the solvent.
- the concentration of solvent in water is 0.1 to 30 weight-%, preferably 1.0 to 20 weight-%, in each case depending on the solvent used.
- the concentration of methanol in water is usually about 1.5 to 15 weight-%, such as 1.6 to 12 weight-%.
- concentration of methanol in water is usually about 1.5 to 15 weight-%, such as 1.6 to 12 weight-%.
- solvent in the cooking stage allows condensation of the resin for a longer time without a too rapid increase in viscosity, and a low level of formaldehyde is achieved.
- lignin is dissolved in a water/methanol mixture, the resin remains soluble for a longer time and enables the control of viscosity during the condensation reaction.
- Other nitrogen bases, such as organic amines can also be used as the catalyst.
- the catalysts are preferably added to the mixture as aqueous solutions having a concentration that varies slightly according to the catalyst.
- concentrations of sodium and potassium hydroxide for example, are between 40 to 60 weight-%, for sodium hydroxide preferably about 50 weight-% and for potassium hydroxide preferably about 46 weight-%.
- the formation of a polymerization chain during the reaction can be influenced through the catalysts by accelerating the condensation reaction between formaldehyde and lignin.
- the catalysts allow for the reacting of virtually all free formaldehyde in a reasonable time, alternatively either at normal pressure or elevated pressure.
- formaldehyde is used in the reaction as an aqueous solution having a formaldehyde concentration of 30 to 60 weight-%, typically 50 to 60 weight-%.
- technical grade formaldehyde is used.
- Technical grade formaldehyde starting material may among other things contain metallic impurities as well as some, typically not more than 12 weight-% methanol.
- the formaldehyde content of the technical grade formaldehyde used is most suitably at least 95 weight- %.
- the process according to the invention for the production of resin involves several stages, comprising 2 to 10 stages.
- the process typically involves 2 to 3 stages, preferably 3 stages, in which case the addition of alkaline catalyst takes place gradually during the process in several stages.
- the gradual addition of alkaline catalyst enables the solids content of the mixture to be kept low during the reaction, allowing for an effective control of the viscosity. This in turn enables the viscosity of the reaction mixture to be kept low enough in order to be able to effectively carry out the condensation reaction.
- “Gradual addition” means that a longer time is used for the addition than would take if a predetermined amount is added at once (i.e. a “one-off addition” is made) without any interruption.
- the duration of addition is usually at least 2 times longer than would be required for a one-off addition, most suitably 5 to 100 times longer, e.g. 10 to 50 times longer.
- the catalyst is usually added in two, three or more portions, in which case the reaction is allowed to proceed after the addition of one catalyst portion before the addition of the next portion.
- lignin is dissolved into a mixture composed of a solvent, especially water and solvent, and the catalyst, especially a water-soluble alkaline catalyst (optionally the first portion).
- Dissolving takes place by stirring the mixture at room temperature (about 20°C) or at an elevated temperature.
- the temperature is usually below 70°C, most suitably below 65°C, for example not higher than 60°C.
- operation takes place at 30 to 50°C, usually at 30 to 35°C.
- Dissolution time is influenced by the chosen reaction conditions and materials, such as the lignin, solvent/solvent mixture, catalyst and the dissolution temperature being used. The dissolution time varies between 0.5 and 2 hours, typically being about 1 hour. When lignin has completely, i.e.
- the temperature of the mixture is raised typically above 60°C, for example about 60 to 100°C, preferably about 65°C, and water is added.
- the calculated amount of formaldehyde is then added gradually while stirring the mixture typically for about 0.1 to 2 hours, preferably for about 15 to 60 minutes.
- the temperature is raised above 80°C, for example about 80 to 100°C, preferably about 85°C.
- the condensation reactions between lignin and formaldehyde take place at this
- the reaction is continued for a period of 0.1 to 2 hours, typically for about 15 to 45 min.
- the second portion of the alkaline catalyst is added, the mixture is cooled to 80°C or below, e.g. to a temperature range of 20 to 80°C, and the condensation reaction is continued. In this way, the condensation reaction can be taken to completion, but if necessary, the second portion of the catalyst can be dosed even in more stages, for example 2 to 5, typically two stages.
- Condensation takes place for a period of about 0,1 to 2 hours, e.g. about 1 hour.
- the third portion of catalyst is optionally added and condensation is again carried out for about 0.1 to 2 hours, e.g. about 1 hour. Operation is continued in a corresponding manner, if the catalyst has been further divided into multiple proportions. After all catalyst has been added, the condensation reaction has been taken into completion.
- the resin being formed is cooled to room temperature, i.e. about 20°C, which is its typical storage temperature.
- the condensation reaction is continued until virtually all formaldehyde has reacted.
- the resin can be cooked in a non-pressurized reaction vessel, i.e. in an ordinary reactor which is operated under normal pressure, or alternatively in a pressure cooker (pressure vessel).
- the condensation reactor is most preferably equipped with devices for heating and cooling the reactor, as well as temperature sensors and temperature control.
- the non- pressurized reaction vessel further most preferably comprises a condenser, such as a vertical condenser, which enables the condensation of the possibly evaporating solvent and its recycling to the reaction vessel. This also ensures that solvent for the resin is always available during the condensation reaction.
- the catalyst system and dry matter influence the rate of development of the viscosity of the resin.
- the dry matter content of the reaction mixture with respect to the resin is typically about 20 to 70 weight-%.
- solvent such as methanol, ethanol or acetone
- the concentration of solvent in the finished resin is typically 0 to 15 weight-%.
- the resin can thus also be recovered in a completely solvent-free form.
- the reaction is continued until all formaldehyde has reacted.
- the reaction is typically continued until a predetermined viscosity is reached.
- the resin formed is collected.
- the resin is typically formulated for further use, as will be described below. "Collecting” comprises also the option that the resin is carried on for further use without isolation or without formulation.
- the Brookfield viscosity of the resin is 20 to 10,000 cP, especially 20 to 1,000 cP, e.g. 20 to 300 cP or 50 to 300 cP.
- the viscosity of the produced resin is on the same level as that of normal impregnation resins.
- a resin having a Brookfield viscosity of 20 to 50 cP is especially suited for impregnation of core paper.
- a resin having a Brookfield viscosity of 100 to 300 cP is in turn suited for impregnation of film paper.
- solvents can also after evaporation be added back to the resin, or the evaporated solvent, such as methanol, ethanol or acetone, can be totally or partly replaced e.g. with water in applications that do not allow the presence of said solvent at all or above a certain limit, such as e.g. over 5 weight-% based on the total weight of the resin.
- the resin produced according to the process is in itself already thermosetting, i.e. addition of additives is not necessary in order to have it formulated into an adhesive.
- the composition of the resin can, however, be further modified, for example by mixing it with extenders and crosslinkers.
- extenders such as amide or amine compounds, such as urea, or monomeric, oligomeric or polymeric carbohydrates, such as sugars.
- crosslinkers such as amine compounds, such as hexamethylene tetramine, or vinyl compounds, such as divinyl benzene.
- the finished resin can be impregnated into the paper as such or formulated with additives and then compressed into a laminate under the influence of heat and pressure.
- a paper impregnated with the resin produced by the process according to the invention or with a resin having a corresponding composition can be compacted into a laminate.
- a multiple opening press can be used, in which compacting takes place under a pressure over 70 bar at about 140 to 150°C.
- the short cycle press used typically comprises 1 to 3 openings and its processing temperature is between 170 and 200°C.
- typical process parameters include a pressure of 20 to 50 bar and a temperature of 170 to 180°C.
- the lignin starting material such as kraft lignin
- the reaction is conducted with formaldehyde, whereby the product of the reaction consists of the reaction product between lignin and formaldehyde.
- the resin was cooked in an ordinary reactor under normal pressure.
- the reaction involved a vertical condenser enabling the condensation of the possibly evaporating solvent back to the reaction mixture.
- water I methanol and catalyst, i.e. the first portion of the catalyst, comprising mere sodium hydroxide or sodium hydroxide in combination with either ammonia or potassium hydroxide, was dosed into the reactor.
- pH of the reaction was 7 to 8.5.
- To this mixture was added the kraft lignin, whereafter the mixture was stirred for about 1 hour, keeping the temperature below 50°C, generally between 30 and 35°C. After stirring, the temperature of the mixture was raised to about 65 °C and water II added.
- the present process can be used for the production of essentially phenol-free impregnation resin, and the resin produced by this process or having a similar composition generally as a substitute for conventional impregnation resin.
- the finished final product can be used as such for impregnating or as a mixture with normal impregnation resins.
- the finished resin can be impregnated into film/core paper (60 to 200 g/m 2 ).
- the amount of resin in the paper varies between 20 to 50 weight- %, in each case depending on the end-use.
- the amount of volatile substances in the impregnate is between 5 and 10 weight- %.
- FIG. 1 Shown in Figure 1, right side, are samples (6 pieces) of finished pressings of lignin impregnates by using different catalyst systems. A reference sample produced from phenol-formaldehyde resin is shown on the left. The present process is especially suited for the production of impregnation resin of core paper and for its use in a compact laminate (Figure 2) as an adhesive.
- Patent literature
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Biochemistry (AREA)
- Materials Engineering (AREA)
- Phenolic Resins Or Amino Resins (AREA)
Abstract
Description
Claims
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FI20175363A FI129275B (en) | 2017-04-21 | 2017-04-21 | Phenol-free impregnation resin |
PCT/FI2018/050286 WO2018193166A1 (en) | 2017-04-21 | 2018-04-23 | Phenol-free impregnation resin |
Publications (1)
Publication Number | Publication Date |
---|---|
EP3612586A1 true EP3612586A1 (en) | 2020-02-26 |
Family
ID=62455525
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP18728202.5A Withdrawn EP3612586A1 (en) | 2017-04-21 | 2018-04-23 | Phenol-free impregnation resin |
Country Status (3)
Country | Link |
---|---|
EP (1) | EP3612586A1 (en) |
FI (1) | FI129275B (en) |
WO (1) | WO2018193166A1 (en) |
Families Citing this family (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN109535441B (en) * | 2018-11-27 | 2021-08-24 | 常州大学 | Preparation method of hydroxymethylated lignin |
CN109679044A (en) * | 2018-12-21 | 2019-04-26 | 上海昶法新材料有限公司 | A kind of preparation method of the modified phenolic resin adhesive suitable for bond paper |
DE102021100142A1 (en) | 2021-01-07 | 2022-07-07 | Suncoal Industries Gmbh | Process for producing a crosslinked lignin with a high specific surface area |
Family Cites Families (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5177169A (en) * | 1989-04-03 | 1993-01-05 | Colorado State University Research Foundation | Method for recovering and using lignin in adhesive resins |
EP0693090A4 (en) * | 1993-04-09 | 1996-07-17 | Alcell Tech Inc | Lignin-based formulations for wood composites |
US20130116383A1 (en) * | 2011-11-03 | 2013-05-09 | Ut-Battelle, Llc | Lignin-derived thermoplastic co-polymers and methods of preparation |
AT513670A1 (en) * | 2012-11-26 | 2014-06-15 | Annikki Gmbh | Process for the preparation of phenol-formaldehyde-resin-analogous polymers |
-
2017
- 2017-04-21 FI FI20175363A patent/FI129275B/en active IP Right Grant
-
2018
- 2018-04-23 WO PCT/FI2018/050286 patent/WO2018193166A1/en active Application Filing
- 2018-04-23 EP EP18728202.5A patent/EP3612586A1/en not_active Withdrawn
Also Published As
Publication number | Publication date |
---|---|
WO2018193166A1 (en) | 2018-10-25 |
FI129275B (en) | 2021-11-15 |
FI20175363A1 (en) | 2018-10-22 |
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