CN101220251A - Oxidized starch modified phenolic resin wood adhesive and its preparation method and application - Google Patents

Abstract

The invention discloses an oxidized starch modified phenol-formaldehyde resin wood adhesive and a preparation method, wherein, the wood adhesive is prepared by firstly compounding molten phenol and formaldehyde into a thermosetting phenolic resin low polymer, then enzymolysis is added into the oxidized starch to obtain oxidized starch substrate, and then a novel environmental protection wood adhesive is attained by modifying the phenolic resin with the obtained oxidized starch substrate. The invention also discloses an application of the wood adhesive in the wood industry. The wood adhesive and the preparation method thereof has the advantages that efficiency is improved and energy is saved by hydrolyzing the oxidized starch with heat resistant-Alpha amylase and by modifying the phenolic resin wood adhesive with the oxidized starch substrate.

Description

Oxidized starch modified phenolic resin wood adhesive and its preparation method and application

technical field

The invention relates to a technology for producing wood adhesives, in particular to a method for preparing wood adhesives by modifying phenolic resin with oxidized starch.

Background technique

The wood industry plays an important role in the economy of many countries. The annual consumption of wood in China reaches 21.5 billion m ³ , which is equivalent to 11.5 billion tons, which is equivalent to the sum of the annual consumption of steel and plastic in China. Due to the lack of forest resources, there are few large-diameter trees, and the wood industry can only use small-diameter wood to glue or make wood-based panels to meet the needs of industry, agricultural production and people's lives. In this way, the wood industry uses glue. volume increased even more.

Generally speaking, the amount of glue used in the general wood industry is: 6t of adhesive is required to ^produce 10,000m3 ^of plywood; 1200t of adhesive is required to produce 10,000m3 ^of particleboard; ^600t of adhesive is required to produce 10,000m3 of MDF; 6t; 30t of adhesive is needed to produce 10,000 pieces of furniture; 70t of adhesive is needed to produce 100t of wood-laminated plastic; 6t of adhesive is needed to produce 10,000 sewing machine tabletops. It can be seen that in the future economic construction, the output of adhesives will be considerable.

With the reduction of petroleum resources, it poses a threat to chemical products that use petroleum as raw materials. The price of fuel is very unstable. Synthetic resins that use petroleum and natural gas resources as raw materials have many uncertainties in the future cost and raw material sources. Therefore, the prospect of synthetic resin has been greatly challenged, thus prompting domestic and foreign researchers to search for substitutes. Free formaldehyde is listed as the number one pollution source by the U.S. Environmental and Resource Protection Agency. In adhesives, the release of free formaldehyde poses a great threat to the environment and the health of workers, and it has increasingly attracted people's attention. Scholars at home and abroad have focused on reducing or replacing adhesives. Many studies have been conducted on the content of phenol and formaldehyde in formulations, or on the development of adhesives based on natural resources.

Starch is a kind of natural polymer material with abundant resources, low price and wide application. It has the characteristics of non-toxic, no peculiar smell and no pollution. After being oxidized, various properties that are easy to control can be obtained, and the starch adhesive itself can be used for bonding paper products and other materials, and can even be used as a wood adhesive after proper modification. After the starch is oxidized and enzymatically degraded, it can be used. Obtain reducing sugars containing aldehyde groups, dextrins, and oxidation or reduction products of these substances, so they can be used to modify phenolic resins under alkaline conditions; from the perspective of comprehensive cost and ease of operation, starch is the best sugar source material ; Oxidized starch itself can be used as an adhesive application, and it has been used in the production of plywood composite glue, so it is feasible to use oxidized starch for the modification of phenolic resin.

Starch is an easy-to-obtain and abundant natural renewable resource. If it can be applied to the production of the adhesive industry, it can increase its added value and broaden the way for its non-food use; in addition, for future adhesives that may face It can be said to plan ahead for the lack of resources, and there is no method for preparing adhesives by hydrolyzing oxidized starch to modify phenolic resins.

Contents of the invention

In order to solve the deficiencies of the above-mentioned prior art, the primary purpose of the present invention is to provide an oxidized starch-modified phenolic resin wood adhesive prepared by utilizing oxidized starch-modified phenolic resin. The invention uses starch, a clean and renewable resource, for the production of wood adhesives, and solves the problems of environmental protection and resource scarcity faced by synthetic resin adhesives.

Another object of the present invention is to provide a preparation method of the above-mentioned oxidized starch modified phenolic resin wood adhesive.

Another object of the present invention is to provide the application of the above-mentioned oxidized starch modified phenolic resin wood adhesive.

In the present invention, a certain amount of molten phenol and a certain amount of formaldehyde are firstly used to synthesize a thermosetting phenolic resin oligomer; then, enzymolysis is added to the dried oxidized starch to obtain an enzymatic hydrolyzate of oxidized starch; A new type of environmentally friendly wood adhesive was obtained by modifying phenolic resin.

The present invention adopts following technical scheme to realize: a kind of preparation method of oxidized starch modified phenolic resin wood adhesive comprises the following steps:

(1) Synthesis of phenolic resin oligomers: In the molten phenol and formaldehyde solution with a molar ratio of 1:1.4 to 1:2.6, add alkali to make the pH value between 9 and 11, then heat up to 60 to 80°C, Keep warm for 40-70 minutes to carry out the addition reaction of formaldehyde and phenol, then raise the temperature to 90-100°C, stir and keep the constant temperature for 20-40 minutes to further condense polymethylol phenol into phenolic resin oligomers; after the reaction is completed, cool down ; Then water, free phenol and free aldehyde are distilled out to obtain a phenolic resin oligomer with a viscosity of about 45-55 mPa.s.

(2) Preparation of oxidized starch enzymatic hydrolyzate: adjust the dried oxidized starch into starch milk with a mass concentration of 25-35%, then add 0.15-0.45% high-temperature-resistant α-amylase, at 74-100°C, React at a pH of 5.5-6.5 for 15-35 minutes, then cool to 20-30°C, then inactivate the enzyme, and evaporate water at 70°C to obtain an oxidized starch hydrolyzate with a DE value of 14-30.

(3) Modification of phenolic resin by oxidized starch: Stir 50-90g of phenolic resin oligomer and heat up to 85-100°C, then add oxidized starch enzymatic hydrolyzate, the phenolic resin oligomer and oxidized starch enzymatic hydrolyzate The mass ratio is 1:1 to 9:1 (wt:wt); then add water to make the solid content between 40 and 60%, stir and react at 85 to 100°C, and keep warm until the viscosity of the solid is 41 ~ 87 seconds, and then cooled to 25 ~ 35 ° C, that is, to obtain wood adhesives.

In order to better realize the present invention, in step (1), the alkali is 50% (wt%) sodium hydroxide solution.

In step (2), the starch milk is first incubated at 95° C. for 5 minutes before adding the high-temperature resistant α-amylase.

In step (2), the enzyme inactivation is carried out by adding NaOH to adjust the pH to 10.

When the amount of oxidized starch added in the step (3) is less than 30% (wt%, based on solids), the water resistance of the prepared modified phenolic resin wood adhesive is good.

The appearance of the oxidized starch modified phenolic resin wood adhesive obtained by the above method is light brown, the solid content is 55%, the free phenol is less than 0.15%, the free aldehyde is less than 1.9%, the dry bonding strength is 1.135MPa, and the wet strength is 0.98MPa. A new type of environmentally friendly wood adhesive.

The application of the above-mentioned oxidized starch modified phenolic resin wood adhesive in the wood industry.

The invention solves the problems of environmental protection and resource scarcity faced by synthetic resin adhesives by using starch, a clean and renewable resource, for the production of wood adhesives. In the present invention, phenol and formaldehyde are reacted to synthesize phenolic resin oligomers; oxidized starch is enzymatically hydrolyzed by high-temperature-resistant α-amylase to obtain oxidized starch enzymolyzate; and then the phenolic resin is modified by the obtained oxidized starch enzymatically Obtaining a new type of environmentally friendly wood adhesive is helpful to solve the environmental protection problems and resource shortage problems faced by resin adhesives.

Compared with the prior art, the present invention has the following advantages and beneficial effects:

(1) The present invention provides a safe, environmentally friendly and low-cost method for producing wood adhesives. The oxidized starch is hydrolyzed by the high-temperature-resistant-α-amylase, and the oxidized starch enzymatic hydrolyzate is used to modify the phenolic resin wood adhesive, thereby improving efficiency and saving energy.

(2) Oxidized starch contains more active groups such as hydroxyl, aldehyde and carboxyl groups, which can react with hydroxymethyl groups in phenolic resins for crosslinking and condensation, thereby modifying phenolic resins. Oxidized starch can replace native starch modified phenolic resin, on the one hand, it can improve the disadvantage of poor water resistance of native starch modified resin, so it can be used as a substitute for urea-formaldehyde resin. On the other hand, modification with oxidized starch can reduce the free phenol and free aldehyde in the resin, and obtain an environmentally friendly phenolic resin wood adhesive.

(3) Proper hydrolysis of oxidized starch by enzymes can reduce its viscosity, increase hydrophilicity and solubility, facilitate the adjustment of the solid content of the adhesive, and thus meet the needs of production. In addition, after enzymatic hydrolysis of oxidized starch, it is more conducive to the combination of active groups in it and the active hydroxymethyl groups in phenolic resin oligomers, thereby further reducing the hydrophilic groups in oxidized starch, which is more conducive to improving the improvement of oxidized starch. Water resistance of starch.

(4) Obtain a wood adhesive with good performance index. The performance indicators of the modified phenolic resin wood adhesive are: the appearance is light brown, the free phenol is less than 0.15%, the free aldehyde is less than 1.9%, the pH value is about 9.5, and the viscosity of Tu-4 is 41-87 seconds. The dry bonding strength of the modified phenolic resin wood adhesive is 1.135MPa, and the wet strength is 0.98MPa. Compared with the unmodified phenolic resin wood adhesive, the free phenol is reduced from 2.23% to 1.89%, and the water resistance does not decrease significantly, which can meet the requirements of type II boards.

Description of drawings

Fig. 1 is the process flow diagram of the method for preparing wood adhesive by hydrolyzing oxidized starch modified phenolic resin of the present invention.

Detailed ways

The present invention will be further described in detail below in conjunction with the embodiments and the accompanying drawings, but the embodiments of the present invention are not limited thereto.

Example 1

As shown in Figure 1, utilize the preparation method of oxidized starch modified phenolic resin wood adhesive, comprise the steps:

(1) Synthesis of phenolic resin oligomers. In a three-necked flask equipped with an electric stirrer, a thermometer, and a reflux condenser (dropping funnel), put molten phenol (37%) and formaldehyde solution with a molar ratio of 1: 2.4 and place them in a constant temperature water bath. Add 50% sodium hydroxide solution from the dropping funnel while stirring to make the pH value 9.5, then raise the temperature to 75°C, keep it warm for 60min to carry out the addition reaction of formaldehyde and phenol, then raise the temperature to 95°C, and keep the temperature for 30min while stirring , to further condense polymethylol phenol into phenolic resin oligomers. After the reaction is completed, cool down to 40°C and discharge; then use a rotary evaporator to distill water, free phenol, and free aldehyde to obtain a liquid with a viscosity of 50 mPa.

(2) Preparation of oxidized starch enzymatic hydrolysis solution. Take the dried oxidized starch and adjust it into starch milk with a mass concentration of 30%, add 0.3% high-temperature-resistant α-amylase, react at 95°C and pH value of 6.0 for 30min, then quickly cool to 25°C, and then inactivate the enzyme , using a rotary evaporator to evaporate the water at 70° C. to obtain a viscous oxidized starch hydrolyzate with a DE value of 25±1.

(3) Modification of phenolic resin by oxidized starch. Weigh 70g of phenolic resin oligomer and put it into a three-necked flask, stir and heat up to 95°C, add oxidized starch hydrolyzate, weigh according to the ratio of phenolic resin oligomer and oxidized starch hydrolyzate 7:3 (wt:wt) Take the oxidized starch enzymatic hydrolyzate, then add distilled water to make the solid content at 45%, stir and react in a 95°C constant temperature water bath, keep warm until the viscosity of the solid is 65 seconds, then cool to 30°C and discharge to obtain Wood adhesive. The infrared spectrum (IR) (Table 1), ¹ H NMR (Table 2), ¹³ C NMR (Table 3) of the wood adhesive is as follows.

Applications of the above wood adhesives in the wood industry:

(1) Bonding strength test

Prepare the standard sample with pine board, which is pre-dried to a moisture content of 15%, and the size is 300mm×300mm×5mm, and the glued surface of the board is planed. Take 100.0g of oxidized starch modified phenolic resin wood adhesive, apply glue on the glued surfaces of the test materials respectively, the amount of glue applied is 140g/ ^m2 (single side), and then put the two pieces of test materials together with parallel grains, and then put Put it into a hot press for hot pressing. The hot pressing temperature is controlled at 140°C, the unit pressure is 1.20MP, and the hot pressing time is 3min. Immerse in water for 3 hours, take it out and cool at room temperature for 10 minutes, measure the width and length of the glued surface of the test piece with a vernier caliper, then clamp the test piece on the tensile testing machine, and load it evenly at a speed of 5880N/min until it breaks.

The bonding strength is calculated according to formula (1-1):

$\mathrm{<span\; class="notranslate">\; \&sigma;</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; p</span>}}{\mathrm{<span\; class="notranslate">\; ab</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

In the formula, σ-adhesive strength, N/mm ² ; p-maximum load when the specimen fails, N; a-length of the glued surface of the specimen, mm; b-width of the specimen, mm.

The dry bonding strength of the modified phenolic resin wood adhesive measured in this embodiment is 1.135Mpa.

(2) Water resistance test

Use the method of bonding strength test to make a standard test piece, made of masson pine material, with a size of 300mm×300mm×5mm. Put the test piece in boiling water for 4 hours, then dry it in an oven at 63±3°C for 20 hours, and then boil it in boiling water for 4 hours , Cool at room temperature for 10 minutes after taking it out, and measure its bonding strength (or wet strength). The water resistance was characterized by the bonding strength at this time.

The water resistance of the modified phenolic resin wood adhesive in this embodiment is represented by the glue strength measured after the wood standard sample is boiled in boiling water for 4 hours, and the measured glue strength (wet strength) is 0.98Mpa.

Table 1 IR(cm ^-1 ) data of modified phenolic resin wood adhesives and phenolic resin ^*

affiliation group   Modified phenolic resin wood adhesive Phenolic Resin -O-CH ₂ -Hydroxymethylphenol, Alcohol Hydroxymethylene Asymmetric Stretching Vibration Stretching Vibration of CH in Methylene Out-of-Plane Bending Vibration of C on Benzene Ring Sugar Ring CH In-Plane Vibration of Sugar Ring CH Sugar On the ring -CH ₂ OH-CH ₂ -O-CH ₂ -ether bond On the sugar ring On the pyranyl ether -CH ₂ -OH On the benzene ring On the 1,2,4,6 substituted structure Sugar ring -CH ₂ -Swing vibration benzene ring ortho-substituted sugar ring   1440102533962931147915981392 no 135312092931, 1209115010771025 no strong 824, 757  No 10163382291614791608 No 1366 No No 2916, 12131148 No 1016883 No No No

^* Test conditions: use the infrared spectrometer of VECTOR 33 of Bruker Company in Germany, adopt KBr tablet method to prepare samples, use KBr as the background film, the resolution is 4cm ^-1 , the number of scans is 32 times, and the wavenumber (σ) range is 400～4000cm ^-1 .

The ¹ H NMR (ppm) analysis ^* of the phenolic resin wood adhesive of table 2 oxidation starch modification*

δ/ppm affiliation group 6.76～7.22 3.24～3.33 (triplet) 3.33～3.47 (doublet) 3.50～3.53 (triplet) 3.63～3.68 (triplet) 3.70～3.73 (doublet) 3.83～3.87 (triplet) 4.39～ 4.60 4.71～4.85 (double peak) 5.11～5.12 (double peak) 5.29 (single peak) H methylene on C ₅ on the phenyl ring methylene sugar ring H methylene on C ₆ on the methylene sugar ring RO-CH ₂ -CH ₂ -Ph active hydroxymethyl, active hydroxymethyl ether linked H on _C3 on the sugar ring H phenolic hydroxyl on _C1 on the sugar ring

^* Test conditions: Solvent: D2O, probe: QNP, D1: 2s, hydrogen spectrum was obtained with AVANCE 400 nuclear magnetic resonance instrument of German Bruker company.

Example 2

Utilize the preparation method of oxidized starch modified phenolic resin wood adhesive, comprise the steps:

(1) Synthesis of phenolic resin oligomers. In a three-necked flask equipped with an electric stirrer, a thermometer, and a reflux condenser (dropping funnel), put molten phenol (37%) and formaldehyde solution with a molar ratio of 1: 2.6 and place it in a constant temperature water bath. Add 50% sodium hydroxide solution from the dropping funnel while stirring, so that the pH value is 11, then raise the temperature to 80°C, keep it warm for 40min to carry out the addition reaction of formaldehyde and phenol, then raise the temperature to 90°C, and keep the temperature for 40min while stirring , to further condense polymethylol phenol into phenolic resin oligomers. After the reaction was completed, the temperature was lowered to 40°C and the material was discharged. Then use a rotary evaporator to distill water, free phenol, and free aldehyde to obtain a liquid with a viscosity of 50 mPa, that is, a phenolic resin oligomer, and place it in a refrigerator to freeze for later use.

Table 3 ¹³ C NMR (ppm) data of phenolic resin and modified resin

^* Test conditions: solvent: D ₂ O, probe: QNP, D1: 2s, carbon spectrum was obtained with AVANCE 400 nuclear magnetic resonance instrument of German Bruker company.

(2) Preparation of oxidized starch enzymatic hydrolysis solution. Take the dried oxidized starch, adjust it into starch milk with a mass concentration of 30%, add 0.15% high-temperature-resistant α-amylase, react at 74°C and pH value of 5.5 for 15 minutes, then quickly cool to 25°C, and then sterilize For the enzyme, use a rotary evaporator to evaporate the water at 70°C to obtain a viscous oxidized starch hydrolyzate with a DE value of 15±1.

(3) Modification of phenolic resin by oxidized starch. Weigh 50-90g of phenolic resin oligomer into a three-necked flask, stir and heat up to 95°C, add oxidized starch hydrolyzate, according to the ratio of phenolic resin oligomer to oxidized starch hydrolyzate 1:1-9:1 (wt:wt) Weigh the oxidized starch hydrolyzate, then add distilled water to make the solid content at 40%, stir and react in a constant temperature water bath at 95°C, keep warm until the viscosity of the solid is 41 seconds, and then cool to 35 °C, the wood adhesive is obtained.

Example 3

Utilize the preparation method of oxidized starch modified phenolic resin wood adhesive, comprise the steps:

(1) Synthesis of phenolic resin oligomers. In a three-necked flask equipped with an electric stirrer, a thermometer, and a reflux condenser (dropping funnel), put molten phenol (37%) and formaldehyde solution with a molar ratio of 1: 1.4 in a constant temperature water bath, and Add 50% sodium hydroxide solution from the dropping funnel while stirring to make the pH value 9, then raise the temperature to 60°C, keep it warm for 60min to carry out the addition reaction of formaldehyde and phenol, then raise the temperature to 100°C, and keep the temperature for 20min while stirring , to further condense polymethylol phenol into phenolic resin oligomers. After the reaction was completed, the temperature was lowered to 40°C and the material was discharged. Then use a rotary evaporator to distill water, free phenol, and free aldehyde to obtain a liquid with a viscosity of 50 mPa.s, that is, a phenolic resin oligomer, and place it in a refrigerator to freeze for later use.

(2) Preparation of oxidized starch enzymatic hydrolysis solution. Take the dried oxidized starch, adjust it into starch milk with a mass concentration of 25%, add 0.45% high-temperature-resistant α-amylase, react at 95°C, pH value of 6.0 for 35min, then rapidly cool to 20°C, and then sterilize For the enzyme, use a rotary evaporator to evaporate the water at 70°C to obtain a viscous oxidized starch hydrolyzate with a DE value of 29±1.

(3) Modification of phenolic resin by oxidized starch. Weigh 50g of phenolic resin oligomer and put it into a three-necked flask, stir and heat up to 85°C, add oxidized starch hydrolyzate, weigh according to the ratio of phenolic resin oligomer and oxidized starch hydrolyzate 1:1 (wt:wt) Take the oxidized starch hydrolyzate, then add distilled water to make the solid content at 45%, stir and react in a constant temperature water bath at 85°C, and keep warm until the viscosity of the solid is 67 seconds. Then cool to 30°C and discharge to obtain wood adhesive.

Example 4

Utilize the preparation method of oxidized starch modified phenolic resin wood adhesive, comprise the steps:

(1) Synthesis of phenolic resin oligomers. In a three-necked flask equipped with an electric stirrer, a thermometer, and a reflux condenser (dropping funnel), put molten phenol (37%) and formaldehyde solution with a molar ratio of 1: 2.4 and place them in a constant temperature water bath. While stirring, add 50% sodium hydroxide solution from the dropping funnel to make the pH value 10, then raise the temperature to 70°C, keep it warm for 70min to carry out the addition reaction of formaldehyde and phenol, then raise the temperature to 95°C, and keep the temperature for 35min while stirring , to further condense polymethylol phenol into phenolic resin oligomers. After the reaction was completed, the temperature was lowered to 40°C and the material was discharged. Then use a rotary evaporator to distill water, free phenol, and free aldehyde to obtain a liquid with a viscosity of 55 mPa.s, that is, a phenolic resin oligomer, and place it in a refrigerator to freeze for later use.

(2) Preparation of oxidized starch enzymatic hydrolysis solution. Take the dried oxidized starch and adjust it into starch milk with a mass concentration of 35%, add 0.45% high-temperature-resistant α-amylase, react at 100°C, pH value 6.5 for 25min, then quickly cool to 30°C, and then inactivate the enzyme , using a rotary evaporator to evaporate the water at 70° C. to obtain a viscous oxidized starch hydrolyzate with a DE value of 26±1.

(3) Modification of phenolic resin by oxidized starch. Weigh 80g of phenolic resin oligomer and put it into a three-necked flask, stir and heat up to 100°C, add oxidized starch hydrolyzate, and weigh according to the ratio of phenolic resin oligomer and oxidized starch hydrolyzate 4:1 (wt:wt) Take the oxidized starch enzymatic hydrolyzate, then add distilled water to make the solid content at 60%, stir and react in a constant temperature water bath at 100°C, and keep warm until the viscosity of the solid is 87 seconds. Then cool to 35°C and discharge to obtain wood adhesive.

Example 5

Utilize the preparation method of oxidized starch modified phenolic resin wood adhesive, comprise the steps:

(1) Synthesis of phenolic resin oligomers. In a three-necked flask equipped with an electric stirrer, a thermometer, and a reflux condenser (dropping funnel), put molten phenol (37%) and formaldehyde solution with a molar ratio of 1: 2.0 in a constant temperature water bath, and Add 50% sodium hydroxide solution from the dropping funnel while stirring to make the pH value 9.5, then raise the temperature to 75°C, keep it warm for 65min to carry out the addition reaction of formaldehyde and phenol, then raise the temperature to 93°C, keep stirring for 30min , to further condense polymethylol phenol into phenolic resin oligomers. After the reaction was completed, the temperature was lowered to 40°C and the material was discharged. Then use a rotary evaporator to distill water, free phenol, and free aldehyde to obtain a liquid with a viscosity of 45 mPa.s, that is, a phenolic resin oligomer, and place it in a refrigerator to freeze for later use.

(2) Preparation of oxidized starch enzymatic hydrolysis solution. Take the dried oxidized starch and adjust it into starch milk with a mass concentration of 30%, add 0.3% high-temperature-resistant α-amylase, react at 85°C, pH value 6.0 for 30min, then rapidly cool to 30°C, and then inactivate the enzyme , using a rotary evaporator to evaporate the water at 70° C. to obtain a viscous oxidized starch hydrolyzate with a DE value of 22±1.

(3) Modification of phenolic resin by oxidized starch. Weigh 60g of phenolic resin oligomer and put it into a three-necked flask, stir and heat up to 90°C, add oxidized starch hydrolyzate, and weigh according to the ratio of phenolic resin oligomer to oxidized starch hydrolyzate 3:2 (wt:wt) Take the oxidized starch enzymatic hydrolyzate, then add distilled water to make the solid content at 50%, stir and react in a 90°C constant temperature water bath, keep warm until the viscosity of the solid is 69 seconds, then cool to 25°C and discharge to obtain Wood adhesive.

The above-mentioned embodiment is a preferred embodiment of the present invention, but the embodiment of the present invention is not limited by the above-mentioned embodiment, and any other changes, modifications, substitutions, combinations, Simplifications should be equivalent replacement methods, and all are included in the protection scope of the present invention.

Claims (7)

1. a preparation method of oxidized starch modified phenolic resin wood adhesive, is characterized in that comprising the steps: (1) Synthesis of phenolic resin oligomers: In the molten phenol and formaldehyde solution with a molar ratio of 1:1.4 to 1:2.6, add alkali to make the pH value between 9 and 11, then heat up to 60 to 80°C, Keep warm for 40-70 minutes to carry out the addition reaction of formaldehyde and phenol, then raise the temperature to 90-100°C, stir and keep the constant temperature for 20-40 minutes; after the reaction is completed, lower the temperature; then distill water, free phenol and free aldehyde to obtain the viscosity 45 ~ 55mPa.s phenolic resin oligomer; (2) Preparation of oxidized starch enzymatic hydrolyzate: adjust the dried oxidized starch into starch milk with a mass concentration of 25-35%, then add 0.15-0.45% high-temperature-resistant α-amylase, at 74-100°C, React at a pH value of 5.5-6.5 for 15-35 minutes, then cool to 20-30°C, then inactivate the enzyme, and evaporate the water at 70°C to obtain an oxidized starch hydrolyzate with a DE value of 14-30; (3) Modification of phenolic resin by oxidized starch: Stir 50-90g of phenolic resin oligomer and heat up to 85-100°C, add oxidized starch enzymatic hydrolyzate; The mass ratio is 1:1~9:1, then add water to make the solid content between 40%~60%, stir and react at 85~100°C, keep warm until the viscosity of Tu-4 of the solid is 41~87 seconds, then cool To 25 ~ 35 ℃, that is, get wood adhesive. 2. a kind of method utilizing oxidized starch modified phenolic resin to prepare wood adhesive according to claim 1, is characterized in that: in step (1), described alkali is 50% sodium hydroxide solution. 3. the preparation method of a kind of oxidized starch modified phenolic resin wood adhesive according to claim 1, is characterized in that: in step (2), described starch milk is earlier at 95 ℃ before adding high-temperature resistant α-amylase Keep warm for 5 minutes. 4. the preparation method of a kind of oxidized starch modified phenolic resin wood adhesive according to claim 1 is characterized in that: in step (2), described inactivating enzyme is to add NaOH to adjust pH to be 10 to inactivate enzyme. 5. an oxidized starch modified phenolic resin wood adhesive is prepared by the preparation method described in claim 1. 6. the described oxidized starch modified phenolic resin wood adhesive of claim 5 is characterized in that: the appearance of described wood adhesive is light brown yellow, and solid content is 55%, and free phenol is less than 0.15%, and free aldehyde is less than 1.9%. The bonding strength is 1.135MPa, and the wet strength is 0.98MPa. 7. the application of oxidized starch modified phenolic resin wood adhesive as claimed in claim 5 in wood industry.