Production of Rigid PU and PIR Slabstock

8/4/2019 Production of Rigid PU and PIR Slabstock

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File No.: PU21020-0409

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InsulationTechnical Information

Production of rigid foam slabstockfrom polyurethane or polyisocyanurateat low investment cost

Siegfried Buschkamp


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Production of rigid foamslabstock from polyurethaneor polyisocyanurate at low

investment cost

Summary

This technical information sheet describes the

minimal resources and equipment required to start

and run polyurethane rigid foam slabstock produc-

tion, for example in developing countries.

Contents

Page

1. General introduction 2

2. Equipment and resources 3

required for operating a slabstock

foaming plant

2.1 Buildings

2.2 Personnel

2.3 Slabstock molds

2.4 Technical equipment and apparatus

2.5 Containers

2.6 Accessories

2.7 Raw materials

3. Procedure 4

4. Example of slab production 5

5. Observations on personnel 7

6. Shed plan 8

7. Suppliers' addresses 9

1. General introduction

This information sheet is intended to show the

minimal expenditure on buildings, equipment and

personnel required for polyurethane rigid foam

slabstock production.

Polyurethane also includes polyisocyanurate rigid

foam, as this is merely a specific variant.

Slabstock manufacture by stirrer mixing offers the

following advantages in addition to the low cost of

investment:

High-viscosity products can be mixed

Formulations can easily be varied

Pastes and colorants can be added

Working by this method does, however, mean cer-

tain disadvantages:

Increased costs through greater losses of

material (residues of about 2 kg in the mix-

ing vessel)

Costs of a polyethylene bag to line the mix-

ing vessel

A considerable amount of air is taken in.

This is generally beneficial as it leads to afine cell structure due to nucleation. Increa-

sed viscosity of raw materials and/or short

cream times can lead to large individual

pores (entrapped air) and lower thermal in-

sulation.

Products with short reaction times are diffi-

cult to process. However, this applies only

very rarely as the reaction times can usually

be adjusted by varying the catalyst content.


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2. Equipment and resources requiredfor operating a slabstock foamingplant

2.1. Buildings2.1.1 Space for production, approx. 100 - 200 m

2.1.2 Space for storage of raw materials and

foam slabstock

2.1.3 Space for cutting and packaging equipment

2.1.4 Extractor on mixing unit Extractor on cutting

machines Extractor on production units,

possibly in storage area

2.1.5 System for keeping raw materials at tem-

peratures as near as possible to 20 - 22 C

2.1.6 Wash basin and eye-rinse water at work-

place

2.2 Personnel (see observations on personnel

under Item 5)

2.3 Slabstock molds (approx. 2 - 3),

e.g. 1 x 1 x 0.8 m, costs of wood + 50 man-

hours + costs for small components

2.4 Technical apparatus

2.4.1 Balance, range up to 200 kg for mixing and

production

2.4.2 Balance, range up to 10 kg for addition of

small amounts (table balance)

2.4.3 Stirrer2.4.3.1 Powerful hand drill (sufficient for blocks up

to 1/2 m3

with low-viscosity raw materials)

2.4.3.2 Fixed stirrer (output approx. 2 - 7 kW)

2.4.3.3 Stirrer discs

2.4.4 Drum lifting truck

2.4.5 Band-saw for trimming and cutting

2.4.6 Paper cutting device

2.5 Containers

2.5.1 Mixing vessel (size: the vessel should be

about half full when it contains the batch)

2.5.2 PE round-bottom sacks to fit mixing vessel2.5.3 Plastic container for rinsing liquid

2.5.4 Measuring beaker for weighing or measur-

ing out additives If the density of the raw

materials is taken into account, balances

can often be dispensed with when using

measuring beakers

2.5.5 Rubbish bags and bins

2.5.6 If 2.5.2 is unobtainable, 2.5.1 should be a

plastic container with which it is possible to

knock out the residues

2.6 Accessories

2.6.1 Protective goggles

2.6.2 Dust filters for sawing

2.6.3 Stopwatch

2.6.4 Rubber gloves

2.6.5 Packaging paper for covering the floor andfor making molds for control pours

2.6.6 Staplers with staples

2.6.7 Scissors/shears

2.6.8 Knives

2.6.9 Felt pens for writing on the foam

2.6.10 Adhesive tape for sticking paper to the floor

2.6.11 Work table approx. 1 x 1m, 80 cm high, for

putting down the accessories and the

measuring beakers for the foam additives

(catalysts, etc.)

2.6.12 Release agent, wax or grease and sponge

2.6.13 Drum-cocks

2.7 Raw materials

2.7.1 Polyol with drum-cock and drum lifting truck

2.7.2 Isocyanate with drum-cock and drum lifting

truck

2.7.3 Blowing agent

2.7.4 Catalyst

2.7.5 Solvents


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3. Procedure

3.1 Prepare and assemble the mold 3 minutes

Apply release wax 2 minutes

3.2 Place polythene bag into mixing vessel 1/2 minute

put in polyol 2 - 5 minutes

(depending on quantity and viscosity)

put in blowing agent 1/2 minute

put in catalyst 1/2 minute

Premix products 1 minute

During the pre-mixing time, fill a separate container

with isocyanate and then, with the stirrer running, pour

it into the polyol and mix 1/2 minute

Carefully pour the reaction mixture into the mold 1/2 minute

Put on lid and secure with wedges 1 minute

Clean stirrer with solvent 1/2 minute

Remove polythene bag with residue (loss from mixing) 1/2 minute

3.3 Mold residence time 10 - 15 minutes

With densities over 60 kg/m3, the slabstock mold should be

opened soon after the fiber time, and at the latest before the

rise time, so the slab can relax without cracking.

Rule of thumb: Slab height in cm = 100 - density

3.4 Demolding the slab 2 minutes

3.5 Take the demolded slab (preferably in batches of

4 blocks per hour) to an external store where they

should remain for at least 5 days 2 minutes

3.6 Cutting: About 40 s are needed for one cut through a

1 m long slab. This gives 28 cuts, each of 40 s, when

cutting up a 70 cm thick slab into 30 mm sheets = 18 2/3 minutes

3.7 Packaging: By the saw there should be a device in

which the sawn sheets can be stacked. This allowssimple packaging.


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4. Example of slab production

The total quantity MA of the batch is obtained from

the volume V of the mold to be filled, the desired

average density RD, the quantity MV of reaction

mix remaining in the mixing vessel and the differ-

ence in buoyancy A between the liquid reaction mix

and the finished foam (= weight of displaced air,

approx. 1.2 kg/m at 20 C) and from the loss MG of

blowing agent occurring during mixing and expan-

sion of the reaction mix.

GVA MMAxVRDxVM +++=

The quantities MK of components are calculated as

follows:

nformulatioperweightbypartsof

MquantityTotalM AK =

Parts by weight of component per formulation

Here is an example:

Volume of molding V = 2.05 x 1.05 x 0.7 = 1.5 m

Desired average density RD = 35 kg/m

Buoyancy difference A = 1.2 kg/m

Quantity remaining in mixing vessel MV 2.5 kg

(determined experimentally)

Loss of blowing agent MG = approx. 0.5 kg

(determined experimentally)

From the foregoing equation, the batch quantity

is:

MA = 1.5 m 35 kg/m + 1.5 m 1.2 kg/m +

2.5 kg + 0.5 kg= 52.5 kg + 1.8 kg + 2.5 kg + 0.5 kg

= 57. 3 kg

Formulation:

100 parts by weight polyol

20 parts by weight blowing agent

2 parts by weight catalyst

120 parts by weight polyisocyanate

242 parts by weight Total

The individual quantities are therefore:

Baymer polyol MPolyol = kg23.68100x242

57.3=

Blowing agent MTM = kg34.7420x242

57.3=

Catalyst MDesmorapid = kg0.4742x24257.3 =

Polyisocyanate MDesmodur = kg28.4120x242

57.3=

The mold in which the foam is formed and cures

can be a wooden box in the simplest case. To sim-

plify demolding, the internal surfaces should be

smooth. Release papers (for example polyethylene-

coated kraft paper or soda kraft paper) may be laid

or stuck in the mold prior to foaming or release

agents (for example release wax) may be used. In

the latter case, the mold walls may be lined with

sheet metal (for example aluminum sheet) or

melamine resin-coated sheets. Release agent sup-

pliers can be found under "Suppliers' addresses".

Slabs are produced as follows:

The mold is set up, and a release agent is applied

to the interior of the walls. The mixing vessel is

balanced, and polyol, blowing agents and catalysts

are poured in and mixed. The components are in-

troduced in the following order: large quantities

before small and low-viscosity products before high-

viscosity products. Finally, the polyisocyanate com-ponent is weighed in or a weighed quantity added.

The components must be mixed thoroughly and

poured into the mold within the cream time which is

sometimes very short (approx. 15 to 40 s).


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Fig. 1: Front elevation of a slabstock mold

Fig. 2: Side elevations and perspective view of a slabstock mold

It is easiest to foam in open molds. The reaction

mix is introduced into a mold (which is open at the

top) where it expands and forms a foam slabstock.

Although the pressure building up on the side walls

is relatively low, it must be allowed for when design-

ing the mold on account of the large areas. With

polyurethane slabstock, pressures of 0.1 bar have

been measured with a density of 35 kg/m and

about 0.15 bar with a density of 60 kg/m. Polyiso-

cyanurate foam develops higher pressures.

The build-up of pressure may be counteracted by

opening the mold 5 to 15 min after foaming of the

block and allowing the foam to expand freely. This

is achieved by loosening the wing nuts of the

screwed rods. The foam slab which now expands

beyond the mold dimensions should be able to


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move unimpeded over the edge of the baseplate. If

the mold is not opened after these short periods, it

is necessary to wait a few hours to prevent the slab

from tearing. The slab should be demolded when

the pressure on the mold has become sufficiently

low, and this moment should be determined ex-perimentally.

The freely rising foam forms a domed surface and

its cells are oriented predominantly vertically (ani-

sotropically). The dome formation, which may result

in a considerable quantity of scrap when cut to size,

may be reduced if the foam is allowed to rise with a

floating lid. Once the reaction mix has distributed

itself on the bottom of the mold and the foaming

process has begun, a lid is placed on top. This lid

floats on the surface of the reaction mix and is

forced up by the foam. The mold can also have a

very simple design here, but should have smooth

internal surfaces to prevent the tightly sealing lidfrom jamming. The rising lid may have to be guided

by hand. The lid normally has a weight per unit area

of about 40 kg/m2.

A completely rectangular slab may be obtained if

the lid abuts against a stop and compacts the foam

slightly.

Fig. 3: Foaming against a floating lid

In some applications, the foam must have only a

very slight cell orientation. This can be achieved by

introducing the reaction mix into a mold which can

be sealed all round and compacts the foam to a

greater extent. The pressure applied to the mold is

correspondingly higher. This foaming under pres-

sure necessitates long mold residence times as the

slabs might otherwise tear.

After production, the slabs are left to cool for at

least 3 to 5 days - usually in an open store - beforesheets or shaped parts are cut from them.

5. Observations on personnel

The number of staff needed for the foaming process

depends on the number of slabs, the size of the

slab and the amount of mix to be processed per

slab. These points, together with the production

time per slab and the quantity of raw materials that

can be processed per year, are given in the table

below.

The figures are based on the assumption that one

man can handle a batch quantity of 30 kg and two

men, one of 80 kg. With larger quantities, a foaming

machine is needed. At least two persons are

needed to put on the floating lid if no crane is avail-

able. When a lid of this kind is used, the amount ofcutting waste is reduced by about 5 % to 15 - 20 %.

A lid should therefore be applied in each case.

A figure of 3 - 5 % has already been included in the

table for the amount of residue left in the mixing

vessel. An overall density of 35 kg/m3

was as-

sumed.


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On a large vertical bench band-saw, one man can

cut up about 20 m3

of foam slabstock in 6 h full

working time. This represents approx. 150 tonnes

per year. Two foaming machine operators produce

as much slab material as two men can cut up on

two bench band-saws (see table). It is thereforeessential to ensure proper investment in the cutting

machines, i.e. considerable automation and per-

haps mill saws should be provided.

6. Shed plan

Fig. 4: Slab production diagram


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7. Addresses of suppliers in Germany

7.1 Laboratory stirrer: Type LM 34

Pendraulik Maschinen und Apparate GmbH

Phillipp-Reis-Str. 3631832 Springe

Tel.: 05041 / 40 61

Fax: 05041 / 50 29

7.2 Production stirrer

Lehmann Maschinenfabrik GmbH, F. B.

Daimlerstr. 12

73431 Aalen

Tel.: 07361 / 5 62 - 0

Fax: 07361 / 5 62 - 60

E-Mail: [email protected]

7.3 Stirrer discs: e.g. Lenart rapid stirrer

Vollrath GmbH & Co., Paul

Max-Planck-Str. 13

50354 Hrth

Tel.: 02233 / 79 89 - 0

Fax: 02233 / 7 87 49

7.4 Round bottom polybags

Nittel GmbH & Co. KG

(Rau) Kelsterbacher Str. 18

65479 RaunheimTel.: 06142 / 94 67 - 0

Polymer-Synthese-Werk GmbH

Landrat-von-Laer-Str. 12

47495 Rheinberg

Tel.: 02844 / 10 - 0

7.5 Drum-cocks

Will & Hahnenstein GmbH Fasstechnik,

Wrmetechnik Anl. Fax: 0271 / 3 75 91 - 25Arnsbacher Weg 5 - 9

57072 Siegen

Tel.: 0271 / 3 75 91 - 0

7.6 Balances

Mettler-Toledo GmbH

Ockerweg 3

35396 Gieen

Fax: 0641 / 5 29 51

Tel.: 0641 / 5 07 - 0

E-Mail: [email protected]

7.7 Release wax

Acmos Chemie GmbH & Co.

Industriestr. 37 + 49

28199 Bremen

Tel.: 0421 / 51 89 - 0

Fax: 0421 / 51 14 15

IGEFA GmbH

Bonnstr. 31

50226 Frechen

Tel.: 02234 / 9 57 21 - 0

Fax: 02234 / 5 21 37

Th. Goldschmidt AG

Goldschmidtstr. 100

45127 Essen

Tel.: 0201 / 1 73 - 01

Fax: 0201 / 1 73 - 18 31

This information and our technical advice whether verbal, in writing or by way of trials are given in good faith but without warranty, andthis also applies where proprietary rights of third parties are involved. Our advice does not release you from the obligation to verify the in-

formation currently provided - especially that contained in our safety data and technical information sheets - and to test our products as to

their suitability for the intended processes and uses. The application, use and processing of our products and the products manufactured by

you on the basis of our technical advice are beyond our control and, therefore, entirely your own responsibility. Our products are sold in

accordance with the current version of our General Conditions of Sale and Delivery.

The methods described in this publication for testing the fire performance of polyurethane and the results quoted do not permit direct con-clusions to be drawn regarding every possible fire risk there may be under service conditions.

Publisher: Business Development Insulation

Bayer MaterialScience AG

D-51368 Leverkusen

www.bayermaterialscience.com

Documents

Production of Rigid PU and PIR Slabstock