Patent Description:
In <NUM>, the global phenol-formaldehyde resin output was about <NUM> million tons, of which the phenol-formaldehyde resin adhesive accounted for about <NUM>%. China is the largest producer of wood-based panels worldwide. In <NUM>, <NUM> million m<NUM> of wood-based panels were produced in China, and about <NUM> million tons of wood adhesives were consumed correspondingly. The wood adhesives mainly include phenol-formaldehyde, urea-formaldehyde, and melamine-formaldehyde resins. The phenol-formaldehyde resin adhesive shows the advantages of high bonding strength, excellent water resistance, and prominent weather resistance due to its unique meshed cross-linked molecular structure, and thus has attracted much attention. However, as there are pros and cons to everything, the raw materials, i.e. phenol and formaldehyde, for producing the phenol-formaldehyde resin adhesive are respectively group <NUM> carcinogen and group <NUM> carcinogen, both of which are highly toxic. Long-term exposure to the phenol-formaldehyde resin will cause serious potential damage to the health of an operator. In addition, when the phenol-formaldehyde resin adhesive is used for hot pressing of panels, a temperature of pressed panels tends to remain high.

With the increasing shortage of petroleum resources and the rising price of petrochemical raw materials, the large-scale production and application of phenol-formaldehyde resin adhesives for wood-based panels are increasingly restricted. Papermaking waste mainly comes from a pulping process of a paper mill. Massive papermaking waste is difficult to be treated, and thus has become a major problem in the papermaking industry.

Therefore, there is an urgent need in the art to develop a phenol-formaldehyde resin adhesive that has a strong binding force among molecules, can reduce the volatilization of phenol and formaldehyde, involves widely-available raw materials, consumes less amount of phenol and formaldehyde, realizes the effective resource utilization, and leads to a low temperature for pressed panels and is suitable as an adhesive in the preparation of a flooring base material.

A technical problem to be solved by the present disclosure: In order to overcome the defects in the art that the preparation of existing phenol-formaldehyde resin adhesives involves large phenol and formaldehyde consumption, an existing phenol-formaldehyde resin adhesive shows weak intermolecular bonding during use such that phenol and formaldehyde volatilize a lot, a temperature of pressed panels is high when an existing phenol-formaldehyde resin adhesive is used for hot pressing of the panels, and the papermaking waste is produced in large quantities and used in small quantities, the present disclosure provides a modified phenol-formaldehyde resin adhesive, and a preparation method and use thereof. In the present disclosure, the modified phenol-formaldehyde resin adhesive is suitable for use as an adhesive in the preparation of a flooring base material. The modified phenol-formaldehyde resin adhesive is synthesized by a staged method, where a papermaking waste is first allowed to initially react with formaldehyde to increase the reaction activity of the structure and improve the reaction efficiency; the papermaking waste is used as a raw material to reduce the consumption of phenol and formaldehyde, thereby achieving the change from waste to treasure; and the prepared phenol-formaldehyde resin adhesive has strong intramolecular interaction, which reduces the volatilization of phenol and formaldehyde and also lowers a temperature for hot pressing.

The inventors have made improvements through a large number of experimental studies during a research and development process, and have found that a composition of the papermaking waste is diverse and complex, including many macromolecular aromatic compounds with benzene rings, which can modify the phenol-formaldehyde resin adhesive to some extent. In terms of the preparation process, the papermaking waste is first allowed to react with formaldehyde to promote the formation of a hydroxymethyl structure, which can effectively increase the reaction activity of the papermaking waste and improve the reaction efficiency, thereby enabling a complete reaction. The use of the papermaking waste can reduce the consumption of phenol and formaldehyde, improve the intermolecular binding to effectively reduce the volatilization of phenol and formaldehyde and reduce the content of free aldehyde, and appropriately reduce a temperature for hot pressing. The papermaking waste is used to modify the phenol-formaldehyde resin adhesive, such that the papermaking waste can be effectively reused and thus changed into treasure, which can not only relieve the pressure that the papermaking waste is difficult to deal with, but also solve the technical problems in the synthesis and later use of existing phenol-formaldehyde resin adhesives and can be used as an adhesive in the preparation of a flooring base material.

The present disclosure adopts the following technical solutions to solve the above technical problem:
The present disclosure provides a use of a modified phenol-formaldehyde resin adhesive as an adhesive in the preparation of a flooring base material, wherein the modified phenol-formaldehyde resin adhesive is obtainable by a preparation method comprising the following steps:.

where steps (<NUM>) and (<NUM>) can be conducted in any order.

In step (<NUM>), the papermaking waste can be a papermaking waste conventionally produced during a papermaking process in the art, which may preferably be one or more from the group consisting of a papermaking slime pulp, a pulp residue, a bark, a grass powder, a silicon-containing white mud, and a spent pulping liquor, and may more preferably be a spent pulping liquor.

A specific preparation method of the spent pulping liquor may include: (a) selecting and pre-steaming a pulping raw material; (b) mixing the pulping raw material with water in a mass ratio of <NUM>:(<NUM>-<NUM>), pumping a resulting aqueous pulping raw material solution with a pump to a top of an independent continuous hydrolysis tower, and subjecting the pulping raw material to a hydrolysis reaction at <NUM> to <NUM> for <NUM> to <NUM>; and after the hydrolysis reaction is completed, collecting a hydrolysate from a lower part of the hydrolysis tower; and (c) cooking the pulping raw material undergoing hydrolysis through a sulfate process as follows: placing the pulping raw material undergoing hydrolysis in a cooking vat, uniformly adding an available alkali to the cooking vat from the top, and cooking at <NUM> to <NUM> for <NUM> to <NUM>, where the available alkali is added at an amount <NUM>% to <NUM>% of an absolute dry amount of the pulping raw material (calculated based on NaOH), the available alkali has a sulfidity of <NUM>% to <NUM>%, and a mass ratio of the pulping raw material to water is <NUM>:(<NUM>-<NUM>); and after the cooking is completed, collecting a dissolving pulp, and filtering the remaining material in the cooking vat to obtain the spent pulping liquor.

Preferably, a preparation method of the spent pulping liquor may include: a. selecting and pre-steaming a pulping raw material; b. mixing the pulping raw material with water in a mass ratio of <NUM>:<NUM>, pumping a resulting aqueous pulping raw material solution with a pump to a top of an independent continuous hydrolysis tower, and subjecting the pulping raw material to a hydrolysis reaction at <NUM> for <NUM>; and after the hydrolysis reaction is completed, collecting a hydrolysate from a lower part of the hydrolysis tower; and c. cooking the pulping raw material undergoing hydrolysis through a sulfate process as follows: placing the pulping raw material undergoing hydrolysis in a cooking vat, uniformly adding an available alkali to the cooking vat from the top, and cooking at <NUM> for <NUM>, where the available alkali is added at an amount <NUM>% of an absolute dry amount of the pulping raw material (calculated based on NaOH), the available alkali has a sulfidity of <NUM>%, and a mass ratio of the pulping raw material to water is <NUM>:<NUM>; and after the cooking is completed, collecting a dissolving pulp, and filtering the remaining material in the cooking vat to obtain the spent pulping liquor.

The pulping raw material may include: conventionally used wood (including Picea jezoensis, Abies holophylla, Picea asperata, Abies nephrolepis, Pinus koraiensis, Larix gmelinii, Pinus massoniana, Populus L. , Betula, Eucalypt, Tilia, and the like), bamboo, grass (rice straw, wheat straw, reed, bagasse, and the like), bast fiber (hemp fiber, mulberry bark, Pteroceltis tatarinowii bark, and the like), and cotton fiber (cotton linter and the like). The pulping raw material may preferably be Eucalypt.

In step (<NUM>), the catalyst may be an alkaline substance conventionally used in the art, which may preferably be an aqueous sodium hydroxide solution with a mass percentage of <NUM>%. The mass percentage refers to a mass percentage of sodium hydroxide in the aqueous sodium hydroxide solution.

In step (<NUM>), the water can be water conventionally used in the art, which may generally be deionized water.

In step (<NUM>), when the papermaking waste accounts for <NUM> parts by weight, the catalyst may account for <NUM> to <NUM> and preferably <NUM> to <NUM> parts by weight, such as <NUM> or <NUM> parts by weight.

In step (<NUM>), when the papermaking waste accounts for <NUM> parts by weight, the water may account for <NUM> to <NUM> and preferably <NUM> to <NUM> parts by weight, such as <NUM> or <NUM> parts by weight.

In step (<NUM>), when the papermaking waste accounts for <NUM> parts by weight, the formaldehyde may account for <NUM> to <NUM> and preferably <NUM> to <NUM> parts by weight, such as <NUM> or <NUM> parts by weight. The formaldehyde may generally be added in the form of an aqueous formaldehyde solution. The aqueous formaldehyde solution may have a mass percentage of <NUM>%, and the mass percentage refers to a mass percentage of formaldehyde in the aqueous formaldehyde solution. The parts by weight of formaldehyde mentioned in the present disclosure refer to parts by weight of formaldehyde in the aqueous formaldehyde solution.

In step (<NUM>), a temperature of the reaction can be a conventional temperature of such an operation in the art, which may be preferably <NUM> to <NUM> and more preferably <NUM> to <NUM>.

In step (<NUM>), a time of the reaction can be a conventional time of such an operation in the art, which may be preferably <NUM> to <NUM> and more preferably <NUM> to <NUM>.

In the present disclosure, after step (<NUM>) is completed, the preparation method may further include a cooling treatment.

Conditions and methods for the cooling treatment can be conventional conditions and methods for such an operation in the art, and the cooling treatment may generally refer to cooling to <NUM> to <NUM> and preferably <NUM> to <NUM>.

In step (<NUM>), the catalyst may be an alkaline substance conventionally used in the art, which may preferably be an aqueous sodium hydroxide solution with a mass percentage of <NUM>%.

In step (<NUM>), when the modified papermaking waste accounts for <NUM> parts by weight, the catalyst may account for <NUM> to <NUM> and preferably <NUM> to <NUM> parts by weight, such as <NUM> or <NUM> parts by weight.

In step (<NUM>), when the modified papermaking waste accounts for <NUM> parts by weight, the phenol may account for <NUM> to <NUM> and preferably <NUM> to <NUM> parts by weight, such as any one from the group consisting of <NUM>, <NUM>, and <NUM> parts by weight.

In step (<NUM>), when the modified papermaking waste accounts for <NUM> parts by weight, the formaldehyde may account for <NUM> to <NUM> and preferably <NUM> to <NUM> parts by weight, such as any one from the group consisting of <NUM>, <NUM>, and <NUM> parts by weight. The formaldehyde may generally be added in the form of an aqueous formaldehyde solution. The aqueous formaldehyde solution may have a mass percentage of <NUM>%, and the mass percentage refers to a mass percentage of formaldehyde in the aqueous formaldehyde solution. The parts by weight of formaldehyde mentioned in the present disclosure refer to parts by weight of formaldehyde in the aqueous formaldehyde solution.

In step (<NUM>), a temperature of the mixing can be a conventional temperature of such an operation in the art, which may be preferably <NUM> to <NUM> and more preferably <NUM> to <NUM>.

In step (<NUM>), the reaction may be conducted in a temperature-programmed manner.

The temperature-programmed manner may refer to raising a temperature to <NUM> to <NUM> within <NUM> to <NUM> and preferably to <NUM> to <NUM> within <NUM> to <NUM>.

After the reaction is completed, step (<NUM>) may further include a cooling treatment.

Conditions and methods for the cooling treatment can be conventional conditions and methods for such an operation in the art, and the cooling treatment may preferably refer to cooling to <NUM> to <NUM>.

In the present disclosure, the modified phenol-formaldehyde resin adhesive may require an outflow time of <NUM> to <NUM> and preferably <NUM> to <NUM> when tested in a TU-<NUM> viscosity cup at <NUM>. The TU-<NUM> viscosity cup is used to test a viscosity of the adhesive according to GB/T1723-<NUM> under conditions for a viscosity test of other related products. That is, at <NUM>, the time for <NUM> of a sample to completely flow out from a hole with a diameter of <NUM> is determined, which is expressed in s.

On the basis of conforming to common knowledge in the art, the above-mentioned preferred conditions can be combined arbitrarily to obtain preferred examples of the present disclosure.

The reagents and raw materials used in the present disclosure are all commercially available.

Beneficial effects of the present disclosure are as follows: in the present disclosure, the modified phenol-formaldehyde resin adhesive is synthesized by a staged method, where a papermaking waste is first allowed to initially react with formaldehyde, which can effectively increase the reaction activity of the papermaking waste and improve the reaction efficiency, thereby enabling a complete reaction; the use of the papermaking waste can reduce the consumption of phenol and formaldehyde in the production of the modified phenol-formaldehyde resin adhesive; and the prepared phenol-formaldehyde resin adhesive has strong intramolecular interaction, which reduces the volatilization of phenol and formaldehyde and the content of free aldehyde, and also lowers a temperature for hot pressing. The modified phenol-formaldehyde resin adhesive is used as an adhesive in the preparation of a flooring base material.

The present disclosure is further described below through examples, but the present disclosure is not limited to the scope of the described examples. The experimental methods in the following examples which are not specified with specific conditions are conducted according to conventional conditions or according to product instructions.

In the following examples, the papermaking waste is a spent pulping liquor, and a specific preparation method of the spent pulping liquor includes: a. selecting and pre-steaming a pulping raw material; b. mixing the pulping raw material with water in a mass ratio of <NUM>:<NUM>, pumping a resulting aqueous pulping raw material solution with a pump to a top of an independent continuous hydrolysis tower, and subjecting the pulping raw material to a hydrolysis reaction at <NUM> for <NUM>; and after the hydrolysis reaction is completed, collecting a hydrolysate from a lower part of the hydrolysis tower; and c. cooking the pulping raw material undergoing hydrolysis through a sulfate process as follows: placing the pulping raw material undergoing hydrolysis in a cooking vat, uniformly adding an available alkali to the cooking vat from the top, and cooking at <NUM> for <NUM>, where the available alkali is added at an amount <NUM>% of an absolute dry amount of the pulping raw material (calculated based on NaOH), the available alkali has a sulfidity of <NUM>%, and a mass ratio of the pulping raw material to water is <NUM>:<NUM>; and after the cooking is completed, collecting a dissolving pulp, and filtering and concentrating the remaining material in the cooking vat to obtain the spent pulping liquor, which has a pH of <NUM>.

In the following examples, Eucalypt chips are used as the pulping raw material.

<NUM> parts of phenol and <NUM> parts of an aqueous sodium hydroxide solution with a mass percentage of <NUM>% were added to a reactor, and stirred and heated for thorough mixing; <NUM> parts of formaldehyde were added at <NUM>, and a resulting mixture was heated to <NUM> within <NUM>; and when a reaction product required an outflow time of <NUM> at <NUM> in a TU-<NUM> viscosity cup, the reaction product was cooled and discharged. The phenol-formaldehyde resin adhesive required an outflow time of <NUM> when tested in a TU-<NUM> viscosity cup at <NUM>.

A manufacturing process of a panel specifically included the following steps:
Glue preparation: A specified amount of the modified phenol-formaldehyde resin adhesive prepared in the above example or the phenol-formaldehyde resin adhesive prepared in the comparative example was thoroughly mixed with an industrial flour of a mass <NUM>% of a mass of the adhesive to obtain a glue for later use.

Glue application: The glue prepared above was poured into a gluing machine, and with a gluing amount of <NUM>/m<NUM> on each side of a veneer, a <NUM>-layer poplar plywood was assembled through interlayer gluing.

Cold pressing: The assembled poplar plywood was placed into a cold press, and a pressure of <NUM> mPa to <NUM> mPa was applied to conduct cold pressing for <NUM> to <NUM>.

Hot pressing: The cold-pressed substrate was placed into a hot press to undergo hot pressing at <NUM>, <NUM>/mm, and <NUM> mPa to <NUM> mPa, and then the pressure was released for <NUM> (until the pressure was <NUM>) to obtain the panel. When the modified phenol-formaldehyde resin adhesive prepared in the example was used to manufacture the panel, a hot pressing temperature was <NUM>, which was relatively low.

In accordance with GBT <NUM>-<NUM>, a strength of the obtained panel was tested. In accordance with the national standard GBT <NUM>-<NUM>, the free aldehyde content in the modified phenol-formaldehyde resin adhesive prepared in the example or the phenol-formaldehyde resin adhesive prepared in the comparative example was tested.

Claim 1:
Use of a modified phenol-formaldehyde resin adhesive as an adhesive in the preparation of a flooring base material, wherein the modified phenol-formaldehyde resin adhesive is obtainable by a preparation method comprising the following steps:
(<NUM>) mixing a papermaking waste, a catalyst, and water, and subjecting a resulting mixture to a reaction with formaldehyde to obtain a modified papermaking waste;
(<NUM>) mixing a mixture of phenol and a catalyst with formaldehyde to allow a reaction to obtain a material A; and
(<NUM>) subjecting the material A to a reaction with the modified papermaking waste, and testing a material obtained from the reaction at <NUM> using a TU-<NUM> viscosity cup, and when an outflow time is <NUM> to <NUM>, collecting the material;
wherein steps (<NUM>) and (<NUM>) are allowed to be conducted in any order and the viscosity is measured according to GB/T1723-<NUM> at <NUM>.