DK151970B - PROCEDURE FOR PREPARING POLYVINYL BUTYRAL AND USING IT IN LAYER GLASS - Google Patents

Description

DK 151970 B

The invention relates to a process for the preparation of polyvinyl butyral by reacting polyvinyl alcohol in aqueous solution with butyraldehyde in the presence of an acidic catalyst, namely a process for preparing this material which enables, at will, to regulate the various properties of importance of the use of polyvinyl butyral in the manufacture of layered glass.

The invention also relates to the use of the manufactured polyvinyl butyral in layered glass.

It is known that polyvinyl butyral is often used as an intermediate layer for layered safety glass, which is used, for example, to make automobile windscreens.

Polyvinylbutyral is usually obtained by a condensation reaction between butyraldehyde and polyvinyl alcohol, the latter being

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2 is prepared by hydrolysis of polyvinyl acetate. By varying the reaction conditions, the amount ratios of the starting materials and the molecular weight of the polyvinyl alcohol used, and by incorporating various excipients and plasticizers, it is possible to vary widely the properties of the final product. Thus, a very large number of variants have been proposed in the practice of the usual methods of preparing polyvinyl butyral in order to modify, depending on the final use of the polybutyral, one or the other of its physicochemical properties.

For the purpose of the use in the manufacture of layered glass comprising at least one layer or film of polyvinyl butyral, in the present invention, emphasis is placed on the following properties which are important for this use (the well known test methods used to evaluate the properties will be described later in the present description): flowability by compression of the layer or film of polyvinyl butyral, resistance to impact of a layered glass comprising such a layer of polyvinyl butyral as an intermediate layer (ball drop test), the strength of the adhesion of polyvinyl butyral to the glass layers. the layered glass (Pummel sample), the transparency of the layered glass (determination of the haze or "turbidity" of the layered glass), and the durability of the layered glass against moisture.

Certain known methods for the synthesis of polyvinyl butyral make it possible to regulate one or the other of the first four properties of the above list, but as far as is known, no method is known which allows simultaneous action of several of these properties and / or on a modification of the resistance to moisture.

In addition, the known plasticizers used in the conventional methods are generally expensive products whose use substantially increases the production price of the layered glass produced from the polyvinyl butyral thus produced.

In the present invention, these drawbacks of the prior art are avoided by providing a process for the production of polyvinyl butyral, which allows to act at will 3

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on one or more, possibly all, of the above-mentioned properties, and which is additionally suitable for the use of plasticizers which are far less expensive than those used in the prior art.

The process of the invention for preparing polyvinyl butyral by reacting polyvinyl alcohol in aqueous solution with butyraldehyde is characterized in that said aqueous solution contains between 8 and 15% by weight of polyvinyl alcohol by incorporating in the solution the acidic catalyst in a proportion of at least 2 5% of the weight of polyvinyl alcohol and an emulsifier in a proportion of 0.15-0.40% of the weight of polyvinyl alcohol to introduce butyraldehyde into the mixture thus obtained, maintained between 5 and 12 ° C. amount sufficient to react with 75-88% of the polyvinyl alcohol in the mixture so that the addition of butyraldehyde occurs gradually over such a period that the polyvinyl butyral precipitates between 10 and 90 minutes after the start of said administration, mixture is stirred for a period of more than 30 minutes at a temperature of from 8-15 ° C, raising the temperature of the mixture to a value between 60 and 80 ° C for a period of between 1 | and 4 hours, when said temperature is obtained, incorporating into the mixture a base to obtain a pH of between 9 and 11, then maintaining the temperature at said value for a period of more than 1/4 hour. and that the precipitated polyvinyl butyral is then separated from the mixture.

In practice, the polyvinyl alcohol used as a starting material advantageously has an acetate content of less than 5%.

Hydrochloric acid is preferably used as an acid catalyst since it is relatively inexpensive. The acid is used in the form of a solution of HCl with a density of 1.18. The amount of this solution used is maintained between 2.5 and 10% by weight based on the polyvinyl alcohol. It has been found that at an amount below 2.5% by weight, the precipitate of polyvinylbutyral, p.v.b. a tendency to block formation, which complicates the separation and washing of this material. Above 10% by weight, a rapid excretion of p.v.b is obtained, with the risk of mass formation of p.v.b. during the precipitation. In addition, the production price of p.v.b. significantly when using excessive amounts of hydrochloric acid.

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As an emulsifier, dodecylbenzene sulfonate can advantageously be used which, as is known, gives a p.v. with acceptable turbidity. The amount of dodecylbenzenesulfonate will, as mentioned, be in milk in limbs 0.15 and 0.40% by weight based on the polyvinyl alcohol. When used | of less than 0.15% by weight, forms in the reactor when heated, blockage, etc., which also occurs at the end of the precipitation in the absence of emulsifier. When more than 0.40% by weight of dodecylbenzenesulfonate based on the weight of polyvinyl alcohol is used, the dodecylbenzenesulfonate tends not to be removed by the washing of the obtained pvb, with poor turbidity of j this material as a result. !

A butyraldehyde amount sufficient to react only with 75-88% by weight of the polyvinyl alcohol present in the mixture is used to obtain a p.v. with good flow properties.

The butyraldehyde is gradually introduced into the polyvinyl alcohol solution having a temperature between 5 and 12 ° C. The delivery duration is preferably maintained between 15 and 60 minutes and is preferably of the order of 30 minutes. It has been found that the rate of precipitation of p.v.b. depends on the supply rhythm of the butyr aldehyde and the precipitation rate of p.v.b. at a feed duration of less than 15 minutes is too high, with a risk of mass formation as a result. At a feed rate of more than 60 minutes, the precipitation rate is too slow, resulting in the formation of blocks which are difficult to wash. A 30 minute duration is preferred, thereby obtaining a powder of p.v.b. of beautiful appearance, whose grain size is particularly suitable for further processing.

The condensation reaction leading to p.v. is exothermic, and the temperature of the reaction mixture therefore rises to a value between 8 and 15 ° C when butyraldehyde is added. The supply rhythm of the butyr aldehyde should be such, depending on the reaction conditions and the duration of the supply of butyraldehyde, that the precipitation is completed between ca. 10 and 90 minutes after the start of the application of the aldehyde.

After the precipitation, it is preferred to allow the mixture to stir for a period of more than 30 minutes at the temperature of 8-15 ° C which it has maintained during the reaction.

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The mixture is then gradually heated to raise the temperature to 60-80 ° C, preferably 70 ° C. The increase in temperature occurs over a period of between 1 1/2 hour and 4 hours, preferably over 2 1/2 hours, which corresponds to a temperature rise of 22 ° C per hour. hour. If the final temperature is lower than 60 ° C, the obtained p.v. obscure, layered glass materials. The same is true when the temperature is above 80 ° C, and in addition, pvb-in block form is formed in the reactor. A final temperature of 70 ° C and a temperature rise of 22 ° C per day. hour is preferred because it results in a p.v.b. of beautiful appearance whose grain size is suitable for the subsequent treatments.

For neutralization of the acidic catalyst at the temperature thus selected and for increasing the pH of the mixture to a value between 9 and 11, sodium hydroxide which is cheaper than the other bases is advantageously used and which nevertheless results in the obtained p.v. have mechanical properties, in particular shock resistance, which are at least as good as those obtained by using other bases such as potassium hydroxide or lime.

After this neutralization, the mixture is kept at the selected temperature between 60 and 80 ° C for a period which may be between 0.25 and 4 hours, and then the mixture is allowed to assume ambient temperature.

The precipitated p.v.b. can then be separated by simple filtration, washed with demineralized water, centrifuged and dried. It has been found that a single wash of the recovered precipitate results in increased turbidity of the final product and that it is preferable to perform at least two consecutive washes and filtrations of p.v.b. More than three consecutive washes only slightly improve turbidity.

The method according to the invention is explained in more detail by the following exemplary embodiments. Of these, Examples no.

2, 3, 4, 6, 7, 8, 9, 10, 17, 32, 33, 34, 35, and 39 comparative examples and labeled with (S).

Before these examples of carrying out the method according to the invention, however, it is to be remembered how the well-known methods of study mentioned previously, which enable assessment of certain properties of p.v.b.

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Compression test for fluidity.

A hot plate press is used for this test.

A test piece of pv. Foil, with a thickness of 0.76 mm (+ 0.01 mm), is cut out in the form of a disc with a diameter of 26 mm. The disc is placed between two 60 x 60 mm thin glass plates. The total test material is placed between the heated plates at 125 ° C in the heated plate press. After 5 minutes of preheating without application of pressure, the test material is subjected for 5 minutes at 10 bar. If D denotes (with an accuracy of 0.25 mm) the diameter of the pressed pvw disk, the flowability is given by the formula: F - ° 26- x x 100

Generally, two measurements are performed on the foil sample.

It is considered that for the use of p.v.b. For the production of a layered glass material, the compression flowability should be at least 60%.

Pummel test (adhesion to glass panels).

The layered glass specimens used in this and subsequent examination methods are prepared as follows. A 760 micron thick pvb film is subjected to prior moisture conditioning, placed between two 30.5 x 30.5 cm glass sheets, after which the layered glass is compressed at a pressure of 10 kg / cm and a temperature of 138 ° C for 20 minutes. One of these specimens is taken for the Pummel test a piece of 150 x 300 mm. This piece is conditioned for 8 hours at -18 ° C. The piece is then placed on a 45 ° inclined surface and beaten with a hammer with a 0.450 kg head with flat web until the glass is powdered. The surface of the sample is approx. 100 x 150 mm and the hammer strokes are distributed over the entire surface. The amount of glass remaining adhered to the polyvinyl butyral film is compared to a Pummel standard scale ranging from 0 to 10.

The test is carried out on the two surfaces of the layered glass, and the result is thus expressed by two values on the Pummel scale, determined as follows: DK 151970B '7% Surface of pvb film, from which the glass Pummel values are detached during breakdown_100 0 95 1 90 2 85 3 60 4 40 5 20 6 10 7 5 8 2 9 0 10

It is considered acceptable for such a layered glass to be tested if the two Pummel values obtained are above 5.

Ball drop test (shock resistance).

This test is carried out with a steel ball weighing 2,270 kg, which is dropped on the central part of a flat specimen of the layered glass, the specimen resting in a horizontal position on a wooden frame. The sample layer of the layered glass measures 305 mm x 305 mm and the glass panels have a thickness of 3 mm.

The samples have a temperature of 21 ° C (+ 2 ° C) and the test is carried out with increasing ball drop heights. The approximate height at which more than 90% of the tested specimens withstand the bullet passes through the layered glass is determined.

This test can be seen as positive when the approximate height is above or equal to 5.2 m.

Test to determine turbidity.

The "turbidity" (or "turbidity") of a transparent layer or foil is defined as the percentage of the luminous flux passing through the plate or foil that is deflected more than 2.5 °.

The measurement of the turbidity is carried out in accordance with NF standard 54-111 (which broadly corresponds to method A of ASTM standard D 1003-61).

For the use of p.v.b. for the production of transparent layered glass, turbidity values below or equal to 0.3% are considered acceptable.

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Moisture Resistance Test.

Layered glass test pieces are prepared by placing a 762 micron plastic intermediate layer between two 30.5 x 30.5 x 0/30 cm glass panels. These specimens are placed in boiling water for 2 hours and then examined for possible formation of blisters or a white translucent band at the periphery of the specimens. If no blisters or white translucent bands are formed, this indicates that the layered glass has successfully passed the test for moisture resistance.

In the following, various examples of the synthesis of polyvinyl butyral are given in accordance with the present invention. In these examples, "layered glass" is meant a glass made by placing a moisture-conditioned pvb plastic interlayer of 760 micron thickness between two 30.5 x 30.5 x 0 glass sheets , 30 cm and compress the total material under a pressure of 10 kg / cm 2 at a temperature of 138 ° C for approx. 20 minutes.

Example 1 In a solution of 30 kg of polyvinyl alcohol in 300 liters of water of a temperature of 10 ° C, 67.5 g of sodium dodecylbenzenesulfonate and 2.65 kg of hydrochloric acid with a density of 1.18 are mixed. 17.1 kg of butyraldehyde is gradually and regularly introduced into the mixture maintained at a temperature of 10 ° C.

An increase in temperature is observed at some degrees.

The solution becomes whitish and its viscosity increases. 28 minutes after the start of introduction of the aldehyde, a precipitate and a decrease in viscosity suddenly appear. The mixture is then left to stand for 90 minutes at a temperature of 13 ° C. Thereafter, the temperature is gradually raised to 70 ° C, with the duration of the temperature rise being 150 minutes. The mixture is then neutralized with 1.35 kg of sodium hydroxide. The temperature is maintained at 70 ° C for 240 minutes. Then the mixture is cooled and filtered. The recovered powder is washed twice, centrifuged and dried.

Laminated glass made with this resin has good optical and mechanical properties as well as good moisture resistance. After being subjected to the moisture resistance test, the layered glass shows each 9

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any white staining or any fuzziness at any point of the sample surface, including the edge of the layered glass.

Samples performed on PVC film prepared from the resin obtained show the following properties: compression flowability: 76%, turbidity: 0.3%, ball drop: 6.1 m

Example 2 (s) In a solution of 30 kg of polyvinyl alcohol in 300 liters of water, 135 g of sodium dodecylbenzenesulfonate and 2.65 kg of hydrochloric acid having a density of 1.18 are mixed. Moreover, the preparation is carried out under the same conditions as in Example 1.

The resin obtained has poor optical properties. The turbidity of the layered material is 0.6% and thus poor.

The example shows the unfortunate influence of an emulsifier content exceeding 0.40% by weight based on the polyvinyl alcohol.

Example 3 (S)

Example 1 is repeated, however, using 33.75 g of sodium dodecylbenzenesulfonate instead of 67.5 g. A very large number of balls are formed in the reactor, and the resin obtained has mediocre properties, especially with respect to turbidity, resulting in ke transparent and more or less whitish layered materials. The example shows the adverse effect of an emulsifying agent content of less than 0.15% by weight based on polyvinyl alcohol.

Example 4 (S)

Example 1 is repeated until precipitation. After maintaining the temperature of 13 ° C, the temperature is raised to 90 ° C. Large blocks are formed in the reactor and the polyvinyl butyral film obtained from the recovered treated resin has a flowability of 58%. The layered material is not transparent. The example shows the adverse effect of heating the reaction mixture to a temperature above 80 ° C after precipitation of p.v.b.

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Example 5 1.5 kg of hydrochloric acid having a density of 1.18 and 67.5 g of sodium dodecylbenzenesulfonate are mixed in a solution of 30 kg of polyvinyl alcohol in 300 liters of water. Initially maintaining the temperature of the mixture at 10 ° C, 16.5 kg of butyraldehyde is introduced over 30 minutes. After precipitation, the mixture is kept at 13 ° C for 90 minutes. The temperature is then raised to 70 ° C and the catalyst neutralized. After holding the mixture at 70 ° C for 240 minutes, the mixture is cooled and filtered. The precipitate is then washed and filtered 3 times, then centrifuged and dried.

The resin thus obtained has a turbidity of 0.3%, and the layered glass produced from this pvb has a ball drop value of 5.8 m, a Pummel value of 9 + 9, and a flowability of 64 %. When subjected to moisture resistance testing, the layered material shows neither white staining nor any blur in any location.

Example 6 (S) In a mixture of a solution of polyvinyl alcohol, hydrochloric acid and sodium dodecylbenzenesulfonate, which is identical to the one used in Example 5 but kept at a temperature of 15 ° C, 16.5 kg of butyraldehyde are introduced. After precipitation and after keeping the mixture at low temperature, it is heated at a rate of rise in temperature of 22 ° C / h. Large blocks then form in the reactor, and the resin obtained gives a fuzzy layered material.

The example shows the unfortunate influence of a starting temperature of the starting materials above 12 ° C.

Example 7 (S)

Example 5 is repeated, however, using 0.5 kg of hydrochloric acid instead of 1.5 kg.

The resin obtained is poorly compatible with the product sold under the name "Flexol", which is used as a plasticizer and the foil produced exudates.

The example shows the unfortunate influence of a catalyst content of less than 2.5% based on polyvinyl alcohol.

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Example 8 (S)

Example 5 is repeated, using the same conditions except for the maximum temperature obtained which is 50 ° C instead of 70 ° C.

The resin obtained gives a cloudy layered material.

The example shows the adverse influence of a temperature for reheating the reaction mixture below 60 ° C after precipitation of p.v.b.

Examples 9 (s) and 10 (S)

Example 5 is repeated until the first filtration of the mixture.

The filtered resin is then washed once, centrifuged and dried (Example 9). The turbidity of the layered material is then 0.7%. The washing is thus insufficient.

When the resin is washed and filtered twice (Example 10), the turbidity is 0.4%.

Examples 11-13 In a solution, at a temperature of 10 ° C, of 30 kg of polyvinyl alcohol of molecular weight 106000 in 300 liters of water, 0.75 kg of hydrochloric acid and 67.5 g of sodium dodecylbenzenesulfonate are introduced. 17.1 kg of butyraldehyde is then gradually added over 30 minutes.

After precipitation, the mixture is kept for 30 minutes at the temperature obtained. It is then heated to 65 ° C and neutralized with 0.405 kg of sodium hydroxide. After holding for 30 minutes at 65 ° C, the mixture is cooled and filtered. Then the resin is washed and filtered, centrifuged and dried.

The film obtained from this resin has a flowability of 61%. A layered material comprising this resin has a turbidity of 0.2%, a spherical aid s value of 7.0 m, and an excellent moisture resistance. It shows no change after being subjected to moisture resistance test.

The test is repeated with a mixture of 27.5 kg of polyvinyl alcohol of molecular weight 106000 and 2.6 kg of polyvinyl alcohol of molecular weight 32000 (Example 12). The test is carried out under the same conditions as in Example 11. The flowability of it from the p.v »b formed. foil produced is 68%.

The experiment is repeated with a mixture of 24 kg of polyvinyl alcohol of molecular weight 106000 and 6 kg of polyvinyl alcohol of molecular weight 12

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j 32000 (Example 13). The flowability of the one with the obtained p.v.b. foil produced is 71%.

Examples 14-25

These examples show the influence of the duration of the precipitation, which depends on the duration of introduction of the aldehyde and also on the temperature of the products at the beginning and on the concentration of the acidic catalyst.

In a first experiment (Example 14), a solution of 39 kg of polyvinyl alcohol in 390 liters of water is cooled to a temperature of 10 ° C.

90 g of sodium dodecylbenzenesulfonate and 3 liters of hydrochloric acid of density 1.18 are added. The mixture, which has a temperature of 10 ° C, is introduced gradually and regularly over 30 minutes 21 kg of butyraldehyde.

A duration of the precipitation (the time from the start of the application of aldehyde to the end of the precipitation) is observed for 28 minutes.

After precipitation, the mixture is kept under stirring at the obtained temperature for 1 1/2 hours. The temperature is then raised to 70 ° for 2 hours and 50 minutes and neutralized with 18 liters of 10 wt% sodium hydroxide solution. After maintaining the temperature at 70 ° C, the mixture is cooled, filtered and washed. After centrifugation and drying, the resin obtained gives a layered material whose optical and mechanical properties are good.

Various plasticizers have been used in conjunction with the resins obtained in the above manner, and no welding from the foil of the softened p.v.b. or incompatibility using "Flexol" [triethylene glycol di (2-ethyl-butyrate)], "Plastolein 90-83" (mixture of esters of C6-C9 ethylene glycols), or of n-hexyl adipate which are relatively inexpensive plasticizers which is not usually used in this technique. j

The layered glass with such pvb film completely consists in satisfying the moisture resistance test, without it any! way is changed (neither white staining nor haze at any point of the j sample, including the edges). j

Example 14 is repeated (Examples 15-25) at a temperature of the polyvinyl alcohol solution of 5 ° C or 10 ° C, an acid quantity of 1.5 µl, 3 liters or 6 liters (4.5, 9 and 18% by weight based on on the polyvinyl alcohol), and a duration of 10 minutes or 30 minutes of aldehyde delivery.

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13 In the following table, the conditions for these different tests are the characteristics of the p.v.b. indicated: - —————— J "~ - ——— ——— 1 '1" -

Examples 14 15 16 17 (S) 18 19 20. 21. .22 .23 24 25 ________ (° C) 10 10 10 10 10 10 5 5 5 5 5 5 HCl (liter) 3 3 6 6 1.5 1.5 3 3 6 6 1.5 1.5 minutes) 30 10 j 30 I 10 30 10 '30 10 30 10 30 j 10 ii * -: —— \ -; - 1 -----—- i—

Time for out- '| ] felling '' | '(minutes) 28' 10 18; 9; 43 25 38 21 27 16 70 41 '-. ! \ i

Presence of o + 0. + +; ++ ++ 0 ++ ++ j ++ grain in fo-; j lien (1) t j ___I__I_I__i______ (1) - 0: no grains - +: some grains - ++: many grains.

Thus, it is seen that depending on the precipitation time, the polyvinylbutyral resin has different appearance and different properties.

A product that is precipitated too slowly shows a large amount of spheres that do not break down during washing and produce poorly softened grains in the foil.

A slow-precipitated resin produces a less supple foil than a rapidly precipitated powder.

When the reaction is carried out with a precipitation time of about 1/2 hour, a powder of very beautiful appearance and with good properties is obtained.

Excessive precipitation gives a non-homogeneous product, which sometimes forms large blocks and may give rise to an unclear layered material. This is the case in most of the examples carried out with 6 liters of acid (18% by weight compared to polyvinyl alcohol).

Examples 26-34

These examples show the influence of the neutralization temperature on the flowability.

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Example 1 is repeated using neutralization temperatures of 70, 80 and 90 ° C, with durations of low temperature maintenance of 1/2 hour, 4 hours or 6 hours, and with duration of maintenance of neutralization temperature of 1 hour, 2 hours. or 4 hours.

The flowability of foils made from the pvb products thus obtained is measured.

The results obtained are given in the following table:!

Neutralization 70 ° c 80 ° c, 90 ° c temperature

Example 26 27 28 29 ~ 30 I 31 32 33 34 j _______ (s) (s) (s);

Low duration! temperature l £ h 4h 6h l £ h 4h 6h l | h j 4h for 6h

Duration at neu-! Ϊ temp. Ih 4h 2h! 2h lh 4h 4h 2h! Ih ---- 1 ----—: -

Flowability 126% 73% 77% j 58% 73% 65% 58% 44% 50%

It turns out that the flowability of the obtained foil is poor when a neutralization temperature of 90 ° C is used while it; is good when a neutralization temperature of 70 ° C is used. j i i i!

Examples 35-42

These examples are intended to show the influence of the neutralization temperature on the properties of the resin and foil.

Example 1 is repeated, however, using neutralization temperatures of 55, 60, 65, and 70 ° C, a low temperature holding period after precipitation between 30 and 90 minutes, a high temperature maintaining after neutralizing between 1 15 and 120 minutes. and a hydrochloric acid amount (density 1.18) between 2.5 µg and 5 wt% based on the polyvinyl alcohol. j The following table lists the experimental conditions and the results obtained. ! j 'i i j

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15

Example Neutralisa- HC1- Duration by Duration J Presence temperature low low temperature after neutralization of grain perature rotation. in the film 35 (S) 55 ° C 3.3% 90 min. 30 min. ++ (1) 36 60 ° C 3.3% 30 min. 60 min. 0 (2) 37 65 ° C 3.3% 60 min. 15 min. ; 0 38 70 ° C 3.3% 45 min. 120 min. 0 39 (S) 55 ° C 2.5% 45 min. 15 min. ++ 40 60 ° C 2.5% 60 min. 120 min. + (3) 41 65 ° C 2.5% 30 min. 30 min. 0 42 70 ° C 2.5% 90 min. 60 min. 0 (1) ++: many grains (2) 0: no grains (3) +: some grains.

Examples 43-50

These examples are intended to show the influence of the duration of maintenance at the neutralization temperature after the neutralization.

Example 1 is repeated, after neutralization, the neutralization temperature is maintained for 15, 30, 60 and 120 minutes, the amount of hydrochloric acid (density 1.18) maintained between 2.5 and 5% by weight based on the polyvinyl alcohol, the duration of maintaining the mixture at low temperature. after precipitation is maintained between 30 and 90 minutes and the neutralization temperature is maintained between 60 and 70 ° C.

In the following table, the conditions used in these experiments are indicated along with the results obtained.

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16 J

"" - "" 1 "" - -> '”<II * I Γ - ..--- -,

Example Duration HC1- Duration Neutral- Ball- Pumble-by-Neu- quantity at low cation drop test tralisation temperature temperature test 43 120 min. 3.3% 45 min. 70 ° C 5.2 m 9 + 9 44 120 min. 2.5% 60 min. at 60 ° C 8.8 m 9 + 9 45 60 min. 3.3% 30 min. j 60 ° C 7.3 m 9 + 9 i j 46 60 min. 2.5% 90 min. j 70 ° C 6.4 m 8 + 8 47 30 min. 5% 60 min. 70 ° C 4.0 m 9 + 9 48 30 min. 2.5% 30 min. 65 ° C 7.3 m = 8 + 9 j 49 15 min. 5% 90 min. 60 ° C 4.0 m j 8 + 8 50 15 min. 3.3% 60 min. 65 ° C 4.0 m 9 + 9

The films made with the pvb products thus obtained have a moisture content close to 0.7. It will be seen that the longer the reaction mixture after neutralization is kept at the neutralization temperature, the greater the probability of a good result in the ball drop test.

! ί j

Example 51 Dissolve 30 kg of polyvinyl alcohol in 300 liters of water and add 2.65 kg of hydrochloric acid of density 1.18 and 67.5 g of sodium dodecylbenzenesulfonate.

When the mixture has a temperature of 10 ° C, 16.5 kg of butyraldehyde is added regularly over 30 minutes.

After precipitation, the mixture is allowed to stir for 90 minutes at a temperature of 13 ° C. Then raise the temperature to 70 ° C for 2 1/4 hours. in

After holding the reaction mixture at 70 ° C for 2 hours, neu-; (the mixture is triturated with 1.35 kg of sodium hydroxide and then kept for 4 hours at 70 ° C. Then cooled, filtered, washed, centrifuged and dried.

The resin obtained gives, softened with [triethylene glycol-! di (2-ethylbutyrate)] ("Flexol") or "Plastolein 90-83" (mixture of

Claims (10)

A process for preparing polyvinylbutyral by reacting polyvinyl alcohol in aqueous solution with butyraldehyde in the presence of an acidic catalyst, characterized in that said aqueous solution contains between 8 and 15% by weight of polyvinyl alcohol incorporating in the solution the acidic catalyst. in a proportion of at least 2.5% of the weight of polyvinyl alcohol and an emulsifier in a proportion of 0.15-0.40% of the weight of polyvinyl alcohol, in the thus obtained mixture kept between 5 and 12 ° C and stirred, butyraldehyde introduces in an amount sufficient to react with 75-88% of the polyvinyl alcohol in the mixture that the addition of butyraldehyde occurs gradually over such a period that the polyvinylbutyral precipitates between 10 and 90 minutes after the start of said addition, that they obtained the mixture is stirred for a period of more aid 30 minutes at a temperature of from 8-15 ° C, that the temperature of the mixture d. then raised to a value between 60 and 80 ° C! for a period of between 1 | and 4 hours, when said temperature is obtained, incorporating into the mixture a base to obtain a pH of between 9 and 11, then keeping the temperature at said value for a period of more than 1/4 hour and that it; precipitated polyvinyl butyral is then separated from the mixture. Process according to claim 1, characterized in that the acidic catalyst is hydrochloric acid. Process according to claim 2, characterized in that the acid used is in the form of a HCl solution of density 1.18. Process according to any one of claims 1-3 / characterized in that the emulsifier is dodecylbenzenesulfonate. 1 Process according to any one of claims 1-5, characterized in that the duration of the supply of butyraldehyde is approx. 30 minutes. Process according to any one of claims 1-6, characterized in that the temperature to which the reaction mixture is heated, after the precipitation of polyvinylbutyral and maintaining mixing temperature, is approx. 70 ° C. j Process according to any of claims 1-7, characterized in that the duration of the temperature rise, after the precipitation of polyvinyl butyral and maintaining the temperature of the reaction mixture, is of the order of 2 1/2 hours. j A method according to any one of claims 1-8, k e n - | characterized by washing the polyvinyl butyral after separation! at least twice. Process according to claim 1, characterized in that the polyvinyl alcohol used as a starting material has an acetate content below 5%. A layered glass with an intermediate layer consisting of polyvinyl butyral, prepared by a method according to any one of claims 1-10. ! ! ]