CN100344720C

CN100344720C - Environment protection, low cost urea resin gel

Info

Publication number: CN100344720C
Application number: CNB200610075047XA
Authority: CN
Inventors: 于红卫; 刘志坤; 槐敏
Original assignee: Zhejiang Forestry College
Current assignee: Zhejiang A&F University ZAFU
Priority date: 2006-03-30
Filing date: 2006-03-30
Publication date: 2007-10-24
Anticipated expiration: 2026-03-30
Also published as: CN1834184A

Abstract

The present invention relates to a production method for urea-formaldehyde resin adhesive having the advantages of environmental protection and low cost. The urea-formaldehyde resin adhesive comprises the raw materials of the following portions by weight: 90 to 110 portions by weight of formaldehyde, 50 to 70 portions by weight of urea 20 to 30 portions by weight of modifier. First, all the formaldehyde and urea accounting for 2/5 of a preparation material are added to a kettle together to be stirred, pH is regulated by NaOH to be 8.5, and temperature is raised to 90 DEG C; second, urea accounting for 1/30 of the preparation material is added, the temperature is kept for 60 minutes, and is cooled to 70 DEG C, and HCI is added to regulate the pH to be 2.5; after prepared adhesive is measured, NaOH is added to regulate the pH to be 7.5; the modifier is added to be cooled to 65 DEG C; the rest urea is added for the third time to react until temperature is naturally cooled to 45 DEG C; the pH is regulated to be 7.0, and the urea-formaldehyde resin adhesive is prepared. The prepared urea-formaldehyde resin adhesive is used for the bonding of bamboo, wood and paper products, and has the advantages of less free aldehyde, low cost, high bonding strength, good water resistance, good prepressing performance and long storage period.

Description

Environment protection, low cost urea resin gel

Technical field

The present invention relates to a kind of urea resin gel.

Background technology

Urea-formaldehyde resin adhesive is the tackiness agent of bamboo and woods such as artificial bamboo board, glued board, shaving board, fiberboard, paper product, but the free formaldehyde content is still higher in the at present general urea-formaldehyde resin adhesive, to the operator and the healthy unfavorable of room resident family of decorateing.The people of numerous strong-willed improvement free formaldehyde releases disguises powder etc. and sets about carrying out development by all kinds of means from improving synthesis technique, substance, glue, reaches effect preferably, but these improvedly close the raising that weak point is a production cost altogether.CN02121076.4 discloses Wang Zhenghong's " making method of environment protection type urea formaldehyde resin adhesive " technology, adopt the traditional technology of weak base---weak acid---weak base and higher temperature of reaction, add trimeric cyanamide and make properties-correcting agent and toughener, make the glue water tolerance and the ageing resistance that make undesirable, production cost is higher.

Summary of the invention

At the above-mentioned deficiency of prior art, the purpose of this invention is to provide a kind of strong acid and strong base and in, low temperature synthetic novel process, can effectively reduce free formaldehyde content and the environment protection, low cost urea resin gel that reduces production costs.

Purpose of the present invention can realize by following measure:

This glue is made up of following raw materials according and weight part thereof: 90-110 part formaldehyde, 50-70 part urea, 20-40 part thickening material; Production technique is the whole formaldehyde that will get the raw materials ready by above-mentioned weight part earlier and accounts for 2/5 amount of getting the raw materials ready urea and add in the reactor, stir, PH=8.0-8.5 with the NaoH regulator solution, carry out addition reaction, be warming up to 90 ± 2 ℃, add the urea that accounts for the amount of getting the raw materials ready 1/30 to reactor again, be incubated 60 minutes, be cooled to 70-75 ℃, add HCI and transfer PH=2.0-2.5, carry out polycondensation, extract reaction solution and splash into when being white in color floss in the beaker that 25 ℃ of water are housed, add NaoH and transfer PH=7.5, add thickening material, be cooled to 65 ℃ again, add the urea of surplus for the third time, react when solution temperature is 45 ℃, transfer PH=7.0.

Purpose of the present invention can also be come perfect by following measure:

In the production technique of this glue, urea divides and joins for four times in the anti-still, and preceding twice add-on and condition add after adding for the second time urea and transferring PH=7.5 with NaoH as hereinbefore for the third time, add-on is the urea that accounts for 1/3 amount of getting the raw materials ready, heat up 90 ± 2 ℃ again, react after 60 minutes, add thickening material again, be cooled to 65 ℃ again, add surplus urea the 4th time and react, when cooling to 45 ℃ naturally, accent PH=7.0.

Said thickening material is at least a in starch paste, carboxymethyl cellulose paste, the sodium alginate paste.

Embodiment

The present invention is described in further detail below in conjunction with embodiment:

The people is known be the formaldehyde and the urea of urea-formaldehyde resin adhesive mol ratio (hereinafter to be referred as UF than) high more, the free formaldehyde content in the glue is just high more, product toxicity is big more, but UF mol ratio＜1.05: 1, the gluing intensity that connects reduces greatly.Under the constant situation of mol ratio, urea is divided into 3-4 time and feeds intake, help reaction, more abundant, make free formaldehyde content low, under highly basic-strong acid-highly basic and lesser temps, carry out polycondensation and help improving bonding strength, so the present invention adopts NaoH, hydrochloric acid or other highly basic, strong acid to regulate pH value, and under 70-75 ℃ of temperature condition, carry out polycondensation.In order to reduce production costs and to reduce free formaldehyde content, the present invention does the material modified of glue with the thickening material of pasty state and is added.Urea divides and adds for three times fashionablely, and the UF mol ratio of each time is respectively: U: F=31: 1,28: 1,124: 1, divide add for four times fashionable, U: F=3: 1,28: 1,16: 1,124: 1, adopt technical pure formaldehyde and urea.Easy to operate for producing, now each raw material is listed as follows by corresponding weight part and gradation add-on:

Consult nine kinds of listed embodiment of table, now illustrate with embodiment 1 and 6.

Embodiment 1:

Earlier with the formaldehyde of 95 weight parts with get the raw materials ready in i.e. 22 weight parts of about 2/5 amount of 55 weight part urea, as the initial dose that adds reactor, stir, PH=8.0-8.5 with the NaoH regulator solution, carry out addition reaction, be warming up to 90 ± 2 ℃, add the urea of the 55 weight part amounts of getting the raw materials ready 1/30 that account for for the second time, promptly about 2 weight part urea react, and are incubated 60 minutes, be cooled to 70-75 ℃, add HCI and transfer PH=2.0-2.5, carry out polycondensation, extract reaction solution and splash into when being white in color floss in the beaker that 25 ℃ of water are housed, add 27 weight part sodium alginate pastes, stir, be cooled to 65 ℃, add for the third time surplus promptly the urea of 31 weight parts react again, naturally be cooled to 45 ℃, accent PH=7.0.

Embodiment 6:

Different with embodiment 1 have 2 points, and the one, the weight part difference of the material that adds, the 2nd, urea changes four addings of branchs into.

Earlier 100 weight parts (hereinafter to be referred as part) formaldehyde and 25 parts of urea are added reactor, stir, PH=8.0-8.5 with the NaoH regulator solution, be warming up to 90 ± 2 ℃, 2 parts of urea are added in the still, be incubated 60 minutes, be cooled to 70-75 ℃, add hydrochloric acid and transfer PH=2.0-2.5, extract reaction solution and splash into when presenting white wadding dress thing in the beaker that 25 ℃ of water are housed, add NaoH and transfer PH=7.5, add 20 parts of urea more for the third time, heat up 90 ± 2 ℃, reacted 60 minutes, add 30 parts of flour pastes, be cooled to 65 ℃ again, add 13 parts of urea the 4th time and react, when being cooled to 45 ℃ naturally, transfer PH=7.0 to get final product the plastic emitting barreled.

All the other embodiment 2-5,7-9, the same procedure by embodiment 1,6 makes this glue respectively.Among nine embodiment, preferred with embodiment 2,5,6,8.

With the glue that this law makes, outward appearance is pale brown look transparent or oyster white colloid, solid content 40 ± 2%, PH=7.0-7.5, free formaldehyde≤0.1%, viscosity 18-22 second (20 ℃ are coated with-4 glasss of mensuration), storage period (25 ℃)＞1 month.

Test shows, the reaction that urea and formaldehyde generate methylolurea is thermopositive reaction, the complete more content of free aldehyde of methylolation is low more, under strong acid condition, reducing temperature (promptly reducing reaction activity) helps hydroxymethylation and reduces content of free aldehyde, add the thickening material of flour paste and so on, not only reduce production costs, and to reduce free cresols content, improve resistance to deterioration, improve bonding strength and water tolerance, the precompressed effect is very remarkable.

The present invention compares the glue that traditional urea resin gel makes, and has free aldehyde and contains Measure the advantage low, that production cost is low, adhesive strength is high, storage period is long and the precompressed performance is good.

Claims

1, a kind of environment protection, low cost urea resin gel is characterized in that this glue is made up of following raw materials according and weight part thereof: 90-110 part formaldehyde, 50-70 part urea, 20-40 part thickening material; Production technique is that the whole formaldehyde that will get the raw materials ready by above-mentioned weight part earlier and the urea that accounts for 2/5 amount of getting the raw materials ready add in the reactor, stir, PH=8.0-8.5 with the NaoH regulator solution, carry out addition reaction, be warming up to 90 ± 2 ℃, add the urea that accounts for the amount of getting the raw materials ready 1/30 to reactor again, be incubated 60 minutes, be cooled to 70-75 ℃, add HCI and transfer PH=2.0-2.5, carry out polycondensation, extract reaction solution and splash into when being white in color floss in the beaker that 25 ℃ of water are housed, add NaoH and transfer PH=7.5, add thickening material, be cooled to 65 ℃ again, add the urea of surplus for the third time, react when solution temperature is 45 ℃, transfer PH=7.0.

2, environment protection, low cost urea resin gel as claimed in claim 1, it is characterized in that in the production technique of this glue, urea divides and joins for four times in the anti-still, preceding twice add-on and condition are as hereinbefore, after adding for the second time urea and transferring PH=7.5, add for the third time with NaoH, add-on is the urea that accounts for 1/3 amount of getting the raw materials ready, heat up 90 ± 2 ℃ again, react after 60 minutes, add thickening material again, be cooled to 65 ℃ again, the 4th time adding surplus urea reacts, when cooling to 45 ℃ naturally, accent PH=7.0.

3, the environment protection, low cost urea resin gel described in claim 1 or 2 is characterized in that said thickening material, is at least a in starch paste, carboxymethyl cellulose paste, the sodium alginate paste.