United States Patent Office 3,720,633

Patented Mar. 13, 1973

2
the mixing kettle or in pipe lines, which results in loss
3,720,633 of the adhesive batch and in expensive downtime.
POLYWNYL ALCOHOL ADHES WE COMPOSITION In order to reduce the danger of gelling in borated poly
WITH HIGH WETTACK CONTAINING A BORON vinyl alcohol adhesive compositions, it has been found
COMPOUND AND A CIS 1,2-POLYOL COM expedient to use a strong water soluble acid such as hydro
POUND
Ralph F. Nickerson, West Springfield, Mass., assignor to chloride acid, acetic acid, phosphoric acid, oxalic acid,
Monsanto Company, St. Louis, Mo. etc., to maintain the pH of the system below 5.5. This
No Drawing. Original application Nov. 12, 1968, Ser. No. approach gives rise to new problems in that this use of
775,170, now Patent No. 3,632,786. Divided and this such acidic materials to control the pH of the system
application Apr. 21, 1971, Ser. No. 136,208 IO causes other difficulties in regard to their storage and
int, C. B32b 27/04, C08b. 25/02; C08d 9/06 handling. Thus, corrosion may occur where these acids
U.S. C. 260-17.4 ST 4. Claims attack the surfaces of the mixing vessels, pumps and the
conduits which are in contact with the adhesive composi
ABSTRACT OF THE DISCLOSURE tions. Such potential corrosion may also involve the adhe
15 sive application equipment, causing pitting of the appli
Disclosed herein is an adhesive composition with high cation rolls, wiping blades and nip rolls, necessitating the
wet tack, which comprises: continued replating or replacement of these parts.
(A) a polyvinyl alcohol resin, Another disadvantage of using acidic materials in bo
(B) a water soluble boron compound, and rated polyvinyl alcohol adhesives is that these materials
(C) a polyol selected from the group consisting of cis 20 attack the cellulosic substrate thereby weakening the very
1,2-polyols and certain 1,3-polyols. material that is to be bonded.
Thus, one uses minimal amounts of these strong acids
for obvious reasons but a small surge of alkali can over
This application is a divisional application of applica come the acid, raise the pH and cause thickening, loss
tion Ser. No. 775,170, filed Nov. 12, 1968 and now U.S.
25 of tack and wetting and ultimate gelling of the adhesive.
Pat. 3,632,786, issued Jan. 4, 1972. Thus, there exists in the art the need for high tack
borated polyvinyl alcohol adhesive compositions which
BACKGROUND OF THE INVENTION do not use strong acids to control the pH of the system.
(1) Field of the invention The present invention surmounts these deficiencies by
30 providing borated polyvinyl alcohol adhesive compositions
This invention relates to adhesive compositions. More without resorting to a strong acid to lower the pH of the
particularly, this invention relates to polyvinyl alcohol system to prevent gelation of the adhesive.
based adhesive compositions having high wet tack, which SUMMARY OF THE INVENTION
adhesive compositions comprise:
35 The present invention relates to borated polyvinyl alco
(A) a polyvinyl alcohol resin, hol adhesive compositions having a high degree of wet
(B) a water soluble boron compound, and tack which comprise:
(C) a polyol selected from the group consisting of 1,2- (A) a polyvinyl alcohol resin,
polyols and 1,3-polyols. (B) a water soluble boron compound, and
40
(2) Description of the prior art (C) a polyol selected from the group consisting of 1,2-
polyols and 1,3-polyols.
Polyvinyl alcohol based adhesives are well known in the The present invention solves problems previously en
prior art. As aqueous compositions having excellent adhe countered in the prior art by providing borated polyvinyl
sive properties polyvinyl alcohol adhesives find widespread 45 alcohol adhesive compositions without resorting to strong
use in bonding cellulosic and other porous materials. Thus, acids to maintain low pH in the system.
polyvinyl alcohol based adhesives are widely used in paper The present invention solves problems previously en
converting applications such as fiber board and box board countered in the prior art by obviating the need for a
laminating, corrugating operations, bag manufacturing and strong acid to lower the pH of the borated polyvinyl alco
in many other applications such as wallboard joint com 50 hol adhesive compositions and accordingly provides high
pounds, wallpaper pastes, bookbinding operations, etc. wet tack adhesive compositions which reduce the danger
High speed gluing and laminating operations require of equipment corrosion, lessen the hazard to operators and
adhesive compositions having a high degree of early wet protect cellulosic substrates.
tack. Wet tack may be defined as the ability of the adhesive It is an object of this invention to provide new adhesive
to develop an initial bond in a short period of time, that 55 compositions.
is, less than 60 seconds, so as to bond the adherents to It is a further object of this invention to provide adhe
gether and hold them until the adhesive bond develops sive compositions with high wet tack and reduced tendency
its full strength. Water soluble boron compounds are well to cause corrosion to metal surfaces.
known additives for polyvinyl alcohol adhesives in order It is a further object of this invention to provide borated
to increase the wet tack of the adhesives as is discussed 60 polyvinyl alcohol adhesive compositions of high wet tack
in detail in U.S. Pat. 3,135,648. but without the need for a strong acid to prevent gelation
However, the use of suitable water soluble boron com of the system.
pounds in conjunction with polyvinyl alcohol adhesives
(hereinafter referred to as borated polyvinyl alcohol) does DESCRIPTION OF THE PREFERRED
increase wet tack but at the same time it causes a tendency 65 EMBODIMENTS
of the adhesive composition to gel if the pH of the system The foregoing and other objects are achieved by adhe
goes above 5.5. As the pH of the polyvinyl alcohol/water sive compositions which comprise:
soluble boron compound adhesive composition increases
above 5.5, the whole adhesive mass thickens with a loss (A) a polyvinyl alcohol resin,
of tack and wetting ability and ultimately sets into a stub 70 (B) a water soluble boron compound, and
born rubbery gel. This gel can cause major operational (C) a polyol selected from the group consisting of 1,2-
difficulties such as the setting up of an adhesive batch in polyols and 1,3-polyols.
 3,720,633
3 4
The polyvinyl alcohols used in the present invention are The inert fillers or extenders can be present in amounts
those partially and fully hydrolyzed materials which con of from about 25 to about 200 parts by weight per hun
tain not more than 60% by weight of residual unhydro dred parts of polyvinyl alcohol.
lyzed acetate groups, calculated as polyvinyl acetate. Furthermore, the borated polyvinyl alcohol/polyol ad
These polyvinyl alcohol materials have viscosities in the hesives of the present invention may be further modified
range of from 1.3 to 150 centipoises when measured as by incorporating therein from 0 to 160 parts by weight
a 4% by weight aqueous solution at 20° C. These mate per hundred parts of polyvinyl alcohol of an additional
rials are well known to those skilled in the art and need binder material such as starch, dextrin and/or synthetic
no further description here. resins such as polyvinyl acetate resins, etc. Especially
The final choice of polyvinyl alcohol used will depend O preferred additional binder materials are starch and poly
on the particular application and the ultimate adhesive vinyl acetate resins which may be used in the form of
properties desired. For example, fully hydrolyzed poly polyvinyl acetate emulsions or aqueous dispersions or in
vinyl alcohols having a 4% aqueous solution viscosity the form of spray-dried polyvinyl acetate powders. The
of at least 35 centipoises would be used in fiber board latter form is to be preferred when the adhesive composi
and box board laminating and in corrugating applica 15 tions are to be in the form of a dry mix adhesive.
tions where a much higher degree of water resistance is The preferred polyvinyl acetate powders used in the
desired and where the application permits the cooking adhesive compositions of this invention are the free-flow
of the adhesive formulation. On the other hand, where ing, water dispersible powders obtained upon spray-drying
cold water soluble adhesives are desired as in wallboard aqueous emulsions of polyvinyl acetate according to the
joint cements, wallpaper pastes, etc., one would use poly 20 process of Morrison, U.S. Pat. 2,800,463 or Bray, U.S.
vinyl alcohol having an aqueous solution viscosity of less Pats. 3,104,234 and 3,225,425 composition prepared in
than 35 centipoises and a residual polyvinyl acetate con the examples set forth below.
tent of from 10 to 40%. The wet tack of the adhesive is determined by placing
For the purpose of the present invention a variety of about two (2) grams of the adhesive on the middle finger,
water-soluble boron compound may be employed. Exam 25 pressing the thumb and forefinger to the adhesive on the
ples of some suitable water-soluble boron compounds are middle finger, and separating the middle finger and the
borax, sodium metaborate, sodium pentaborate, boric acid, forefinger from the thumb, thus stretching the adhesive.
disodium octaborate tetrahydrate, boric oxide, etc. The degree of cohesion as judged by the legging or string
Especially preferred boron compounds are boric acid ing of the adhesive and the sound produced as the ad
and partially neutralized borate salts especially those with 30 hesive separated were observed and a rating of from 0
a low degree of neutralization. The amount of water-solu to 100 was given to the adhesive. The adhesive having
ble boron compound to be employed will depend to some the least tack was one having the lowest value, while the
extent on the application for which the adhesive is to be adhesive having the most tack was the one having the
used and upon the form of boron compound which is highest value.
employed. In general from 2 to 30% parts by weight of 35 The quick tack of the adhesive compositions is also
the water soluble boron compound, per hundred parts of determined by applying a 1.0 mil coating of adhesive to
the polyvinyl alcohol, is used in the practice of the pres a strip of white paper of the type commonly used in office
ent invention. More preferably, one would use from 4 to duplicating equipment, laminating this immediately to an
15% parts by weight of the water-soluble boron com other strip of the same type paper, rolling the laminate
pound per hundred parts of the polyvinyl alcohol. How 40 assembly with a 5 lb. rubber roller and then periodically
ever, the maximum amount of the water-soluble boron delaminating the assembly by stripping one sheet of the
compound used should not exceed 1.5% by weight, ex paper from the other and noting the time to 100% paper
pressed as boric acid, based on the weight of the aqueous failure.
adhesive composition. The following examples are set forth in illustration of
The polyols used are cis 1,2-polyols such as sorbitol, 45
the present invention and should not be construed as a
mannitol, glycerol, dulcitol, ethylene glycol, etc., and 1,3- limitation thereof. All parts and precentages are by weight
polyols such as pentaerythritol, trimethylol ethane, tri unless otherwise indicated.
methylol propane, trimethylol butane, etc. Especially pre EXAMPLE 1.-CONTROL
ferred are sorbitol, mannitol and glycerol. Although poly This example is set forth to illustrate the low initial
vinyl alcohol may be classed as a polyol, the expression 50 tack of polyvinyl alcohol adhesives that do not contain
polyol as used in regard to the present invention refers water-soluble boron compounds.
to those classes of polyols referred to above. Ten (10) parts of the polyvinyl alcohol resin having
The amount of the polyol component used in the poly a 4% aqueous solution viscosity of 57 centipoises at 20
vinyl alcohol adhesives of the present invention is in the C. and a residual acetate content of less than 1.8% by
range of from 2 to 40 parts per hundred parts polyvinyl 55 weight are dry blended with 1.8 parts of sorbitol. This
alcohol resin (p.h.r.) More preferably from 5 to 25 parts dry blend is then slurried in 88.2 parts of cold water and
of the polyol component is used per hundred parts of then cooked at 95° C. to effect solution of the resin. The
resin (p.h.r.). In the most preferred embodiment 10 to resulting solution has a pH of 5.8 and relatively low
20 parts of the polyol component are used per hundred wet tack when compared to those adhesive compositions
parts of resin. described below which contain a water-soluble boron com
The water-soluble boron compound and the polyol used 60
pound.
in the present invention may be in the form of dry pow EXAMPLE 2
ders or crystals or in solution form. The former is to be This example is set forth to illustrate that the presence
preferred in dry mix type adhesives. of a small amount of a polyol in the boron compound
The adhesive compositions described above can be used 65 containing polyvinyl alcohol adhesive will prevent gel for
as is or in conjunction with various inert fillers or ex mation and provide a high wet tack adhesive.
tenders. These extenders and fillers are well known to Example 1 is repeated here except that 1.2 parts of boric
those skilled in the art. Examples of these materials in acid are dry blended in with the polyvinyl alcohol and
clude clay, especially kaolinite clays, dolomite, ground Sorbitol components. This blend is then slurried in 87.0
limestone, i.e., calcium carbonate, asbestos, mica, silica, 70 parts of water and cooked as in Example 1. Upon cool
talc, gypsum, etc. ing, the adhesive composition is found to have a pH of
In addition to lowering adhesive costs the inert fillers 4.8 and high wet tack.
and extenders are useful for controlling adhesive viscosity EXAMPLE 3
and penetration of the adhesive into the substrate as well Example 2 is repeated here except that the amount of
as promoting quick tack, i.e., setting of the adhesive bond. 75 Sorbitol is increased to 3.6 parts and the amount of water
 3,720,633
5 6
is decreased to 85.2 parts. The resulting adhesive, which than similar compositions which do not contain a polyol
has a pH of 4.4, is found to have high wet tack properties. component.
The following Examples 6 to 8 are set forth to further
EXAMPLE 4 illustrate some of the variations that are possible within
Example 3 is repeated here except that mannitol is sub 5 the scope of this invention. These examples are to be
compared with Example 9 that does not contain a polyol
stituted for the sorbitol used in Example 3. The resulting compound in accordance with the practice of this in
adhesive has a pH of 4.6 and high wet tack properties. vention. In each example the polyvinyl alcohol used is
a fully hydrolyzed material having a residual acetate
O content of less than 2% and a 4% aqueous solution vis
TABLE I cosity of 62 centipoises when measured at 20° C. The
Example clay used is a kaolinite clay which is slightly alkaline
in nature.
2 3. 4.
In each example the ingredients are dry blended and
Ingredients: i
Polyvinyl alcohol---------- 10 10 10 O
5 cooked as in Example I. Laminates are then prepared
Boric acid---------------------------- .. 2 2 2 and tested as in Examples 3 to 5 above, and the results
Sorbitol-------------- 1.8 1.8 3.6 ---------- are tabulated in Table II below.
Mannitol------------------------------------------------- 3.6
Water- 88.2 87 85.2 85.2
pH--------- 5.8 4.8 4.4 4, 6 TABLE II. SUMMARY OF EXAMPLES 6 TO 9
Wet tack--- 27 75 70 70
Quick tack (seconds)? 70 50-55 50-55 50-55 20 Example
1 Parts by weight. A3, 6 7 8 9
2 Time to 100% paper failure. Ingredients:
Polyvinyl alcohol.--------- 5.0 5.0 5.0 5.0
Boric acid------------------ 0.5 0.6 2 .. 2
25 Sorbitol-------------------- 5 0.6 1.2 ----------
The data in the foregoing Table I illustrate the Su Clay------------------------
Water
5.0
78.0
15.0
78.8
5.0
7.6 78.8
5
perior adhesive compositions that are obtained when a pH------ 4.9 4.9 4.7 Ge.
water-soluble boron compound and a polyol are used in Wet tack
Quick tack
77
35-40
82
35-40
76
35-40
<10
(8)
conjunction with the polyvinyl alcohol resins of the pres
ent invention. i Parts by weight.
30 2 Seconds to 100% paper failure.
The adhesive compositions prepared in Examples 2 8 Unable to test.
to 4 above were used to laminate two sheets of 64 lb.
kraft paper together using a 5 mill coating of adhesive. Examples 6 to 8 are fluid stable adhesives with ex
The adhesive compositions machined very well and pro cellent wet tack and quick tack. Example 9 which is
vided an adhesive bond with high initial wet tack. The 35 prepared without using a polyol compound in accord
laminates were then dried overnight at room tempera ance with the practice of this invention is an unusable
ture and then were soaked for 48 hours in Water at room gel.
temperature. The wet laminates were then subjected to EXAMPLE 10
delamination tests. In each sample the delamination was
due to paper failure and not to deterioration of the glue 40 This example is set forth to illustrate the use of an
line. additional binder material in the adhesive formulations
EXAMPLE 5.-CONTROL of the present invention. The following formulation is
This example is set forth as a control to illustrate the used in this example.
pronounced tendency of boron compound containing Parts by weight
polyvinyl alcohol adhesives to gel unless the pH of the Polyvinyl alcohol --------------------------- 4.6
Boric acid --------------------------------- 0.5
system is maintained below a pH of about 6. Sorbitol ----------------------------------- 0.5
Ten (10) parts of a fully hydrolyzed polyvinyl alcohol Clay -------------------------------------- 11.2
resin having a 4% aqueous solution viscosity of 57 cen Pearl starch -------------------------------- 2.2
tipoises at 20° C. and a residual acetate content of less 50 Water ------------------------------------ 81.0
than 1.8% by weight is dry blended with 1.2 parts of
boric acid. This dry blend is then slurried in 88.8 parts Parts total --------------------------- 100.0
of cold water and then cooked at 95 C. to effect solu
tion of the resin. The resulting adhesive solution is found The polyvinyl alcohol used is the same as that used
to have a pH of 5.5 and a wet tack rating of 75 and is in Example 1 above. The dry ingredients are dry blended,
generally comparable to the adhesive composition of 55 slurried in cold water and then cooked as in Example 1.
Example 2 in physical properties. This adhesive composition is found to have a pH of
Simulated alkali contamination of the adhesive com 5.1, a wet tack rating of 78 and a quick tack rating of
positions of Examples 2 and 5 was effected by introduc 30-35 second. Laminated fiber board made with this
ing a 5% borax solution into each adhesive composi 60
material is found to have excellent water resistance.
tion. EXAMPLE 11
Fifty (50) ml. of borax solution per liter of aqueous Example 10 is repeated here except that the pearl starch
adhesive composition are added to the polyol containing is replaced with a spray-dried polyvinyl acetate powder.
adhesive prepared in Example 2, with only a moderate
increase in viscosity and with no loss of Wet tack or The resulting adhesive composition is comparable to that
wetting ability. Similar results were obtained with the 65 obtained in Example 10.
aqueous adhesive compositions prepared in Examples 3 The following Examples 12 to 16 are set forth to fur
and 4. ther illustrate the wide variation that can be made in the
On the other hand, one liter of the aqueous composi adhesive compositions of the present invention. Tn each
tion prepared in Control Example 5, which contains no example the ingredients are slurried in water and cooked
polyol component, gels into a rubbery mass with loss 70 as in Example 1. The resulting adhesive compositions
of wet tack and wetting ability when only 10 ml. of the are stable solutions with a high degree of wet tack and
borax solution is added. good adhesive properties. The compositions of these ma
These experiments clearly indicate that aqueous ad terials are outlined in the following Table III. The values
hesive compositions of the present invention are less sus in parenthesis indicate the parts by weight of the re
ceptible to gelling when contaminated by alkalimaterials 75 spective compounds per hundred parts by weight of the
 3,720,633
7 8
polyvinyl alcohol used, which is the same type of poly- (D) from 25 to 200 parts by weight of an inert filler
vinyl alcohol as was used in Example 1. selected from the group consisting of clay, dolomite,
The polyvinyl acetate used is a spray dried dextrin calcium carbonate, asbestos, mica, silica, talc and
stabilized material and the clay is of the kaolinite variety gypsum; and
which is further identified as ASP-600 (a trademark of (E) from 0 to 100 parts by weight of additional binder
the Minerals and Chemicals-Philipp Corp.). The material selected from the group consisting of starch
amount of water used in each example is adjusted to and dextrin.
give 1500 parts by weight of the aqueous adhesive com- 2. The adhesive composition of claim 1 wherein the
position. polyol is sorbitol, and the boron compound is boric acid.
TABLE III.--SUMMARY OF EXAMPLES 12 TO 16 ADHESIVE COMPOSITIONS
Example Boron compound Polyol File Additional binder
12----------- Boric oxide (10)------- Trimethylol propane (20)---------------------
13-- - Boric acid (16) Glycerol (15) Clay (100)
14. - Boric oxide (20) Sorbitol (25)--------------------------- Pearl Starch (50).
15.-- - Boric acid (20) Glycerol (15)--------------------------- Polyvinyl acetate (50)
16----------- Boric acid (30)-------- Mannitol (40).-- Clay (100).------- DO.

The ability of the polyols used in the present inven- 3. The adhesive composition of claim 1, wherein the
tion to prevent gelation of the borated adhesive com- polyol is mannitol.
positions is quite unexpected especially when one con- 20 4. A dry blended adhesive composition consisting es
siders that the pH of a 5% solution of a polyol, e.g., sentially of:
sorbitol is 6.3 which is essentially the same as the pH (A) 100 parts by weight of a polyvinyl alcohol having
of distilled water. not more than 60% by weight of residual unhv
The bland non-corrosive nature of these polyols makes drolyzed polyvinyl cele R EE
them especially desirable and useful as additives in 25 d
borated polyvinyl alcohol adhesive compositions. solution
to viscosity at 20° C. in the range of from
150 centipoises; 1.3
1
Also ted for use in
contemplated in the practice of
the practice this inve
of this inven (B) from 2 to 20 parts by weight of boric acid;
tion are other adjuvants which are commonly used in s
adhesive formulators such as preservatives, fungicides, (C) from 2 to 40 parts by weight of a cis 1,2-polyol
fluidizing agents, antifoam agents, viscosity regulators, 30 selected from the group consisting of sorbitol and
humectants, plasticizers, solubilizing aids, pigments, dyes, mannitol;
odor masking compounds, etc. (D) from 25 to 200 parts by weight of clay; and
From the foregoing it should be apparent that many (E) from 0 to 100 parts of additional binder material
modifications and variations may be made in the practice selected from the group consisting of starch and
of the present invention without departing from the Spirit 35 dextrin.
and scope thereof.
What is claimed is: References Cited
e f, i. blended adhesive composition consisting eS- UNITED STATES PATENTS
Sea
(A)not100more
partsthan
by weight of a polyvinyl alcohol having 40 3,425,972
60% by weight of residual unhy-
2/1969 Nobile et al. --- 250-174 ST
3,600,342 8/1971 Nickerson et al. -- 260-17.4 ST
drolyzed polyvinyl acetate groups and a 4% aqueous 3,632,786 1/1972 Nickerson ---- 260-17.4 ST
solution viscosity at 20° C. in the range of from 1.3
to 150 centipoises; WILLIAM H. SHORT, Primary Examiner
(B) from 2 to 20 parts by weight of a water soluble 45 E. WOODBERRY, Assistant Examiner
boron compound selected from the group consisting
of boric acid, boric oxide and borax; U.S. C. X.R.
(C) from 2 to 40 parts by weight of a cis 1,2-polyol 106-210, 214; 161-250, 266; 260-33.4 R
selected from the group consisting of sorbitol and
mannitol;